Steve Young is by far the best left-handed quarterback of all time, as well as the player to best combine passing and rushing in NFL history, or at least since the 1930's. In his time, he was a unique combination of accuracy and skill in passing, and speed and power in running . Even in the modern heyday for the running quarterback, only Aaron Rodgers has been as good at both passing and running.
Even with all of that going for him, Young is also one of two quarterbacks to disappoint media and fans everywhere by winning "just" one Super Bowl. (You know the other one.)
But Young's qualitative greatness is almost off the charts. A flood of numbers will demonstrate as much. (Click here for what the abbreviations mean.)
Of the 73 players to pass at least 400 times from 1991-98, Young led them all with a 130 ANY/A+ (30% better than average), and that doesn't even measure his rushing value. Who was second? Dan Marino. With a 116. Young also had a 130 Y/A+ in that time period. Chris Chandler was second...at 112. Passer rating index? Young led with a 133; Brett Favre was second at 116. Not only is Young leading everyone in these stats, he's leading them by a mile, and different players are ranking second depending on which efficiency measure you choose. There's no such dilemma with Young. Pick one, he was the best, and it wasn't close. 
Here is a scatter plot with Y/A+ on the horizontal axis and ANY/A+ on the vertical:
Yes, Young is represented by that lonely dot in the upper right. That's what I meant by "almost off the charts." Any questions?
And recall how low the attempts threshold is here--400 in eight seasons. At 300, Doug Flutie's 1998 season enters the sample, and it exceeded Marino's 1991-98 ANY/A+ mark, with a 121--still way lower than Young's 1991-98 mark.
In fact, how low do you have to set the bar for attempts before someone actually surpasses Young in any of these three indices? 142. Rob Johnson's Y/A+ then beats Young's...and he still falls short in Rate+ and ANY/A+. To finally approach Young in the other figures, you need to set the minimum attempts to: 44, to reach Mark Vlasic's 1991 season, which touches Young's 1991-98 stretch with a 133 Rate+ and 129 ANY/A+. But to finally conquer Young, to beat him by as much as he beat second place in the more legitimate samples, try 17, when Shane Matthews posted a 167 Rate+ and 169 ANY/A+ in two relief appearances for the 1996 Bears. By this time, Marino has fallen from second with a 116 ANY/A+ to tenth.
How good is a 130 ANY/A+, by the way? Well, five quarterbacks have posted a 130 ANY/A+ in a single season (link here to full numbers):
- Brett Favre, 1995 (MVP, 1st Team All Pro)
- Ron Jaworski, 1980 (Pro Bowl)
- Peyton Manning, 2005 (1st Team All Pro)
- Donovan McNabb, 2004 (Pro Bowl)
- Kurt Warner, 2001 (MVP, 1st Team All Pro)
That's three 1st Team All Pro seasons, and the other two seasons were career years for Jaworski and McNabb. And it's a level Young played at for eight years.
Young's dominance also comes through when looking at individual seasons. He often led the league in a large assortment of statistics: completion percentage 5 times, TD% thrice, INT% twice, yards per attempt 5 times, adjusted yards per attempt 6 times, net yards per attempt 5 times, and adjusted net yards per attempt 4 times. Each of those numbers you see that are four or higher mean he led the league in the statistic at least as often as every other QB in the league combined during his 8 year peak.
Additionally, his rating was at least 20% above average every single year, and his ANY/A at least 16% above average. Recall Marino was second from 1991-98 in ANY/A+ with a 116. So Young's worst ANY/A in that time frame was as good as the second best ANY/A in the league across all eight seasons. In other words, by adjusted net yards per attempt, Young's worst season was still as good as the league's next best quarterback was on average.
And you probably don't need me to tell you that, on top of all that, Young was also rushing for 350 yards and 4 touchdowns on 6 yards per carry every year.
The Associated Press also recognized Young for what he was during this time: one of the two best quarterbacks in the league pretty much every season. From 1992-94, he was 1st Team All Pro three times. He was then 2nd Team All Pro in 1995, 1997, and 1998. (Favre was 1st Team from 1995-97, but in 1998, Randall Cunningham took that honor home.) This compares very well to some high-profile contemporaries: Elway made 2nd Team three times his entire career (1987, 1993, 1996), and never first; Aikman never made so much as 2nd Team All Pro .
The main argument against Steve Young's silly dominance in this time period is that he had the greatest receiver of all time to throw to. Well, except in 1997, when his #1 target was a second-year receiver by the name of Terrell Owens , who caught 60 passes. And Young still led the league in passer rating and ANY/A. By passer rating, it was also his best non-MVP season.
Some also criticize Young for not putting up volume statistics. However, he led the league in touchdown passes four times and yards per game twice, and threw for 4,000 yards twice, something his predecessor never accomplished.
Some criticize Young's durability, as he started 112 of 128 possible games in these eight seasons, effectively missing a full season. Admittedly, this is not a pristine mark, but he still started 16 games three times, 15 games twice, and 10, 11, and 12 games in the other three seasons. He wasn't missing a large chunk of games every year.
Others hold Young's time in Tampa Bay against Young. We'll get to that later, but for now, an observation: people tend to allow great quarterbacks their terrible early seasons on terrible teams, so long it's the same teams that got better as the quarterback did. John Elway gets away with his rookie year with Denver. Terry Bradshaw gets this benefit regarding his ghastly first two seasons in Pittsburgh. And Aikman's bad first two seasons are not held against him, as Dallas gradually started winning again.
It was Aikman's Cowboys teams, plus the Montana legacy, that led to criticisms of Young's inability to win in the playoffs early in his tenure as San Francisco's starter. Aikman often rates higher than Young in rankings of quarterbacks , but this essentially occurs on account of the 2-1 record Aikman's Cowboys had vs. Young's 49ers in the playoffs. It's kind of silly to effectively make a single game out of hundreds the difference in your ranking, but it happens. (It happened in early days of the Manning-Brady debate, too.) But a closer look at each game makes it really difficult to turn Young into the main scapegoat, especially considering that Dallas entered both games with the better defense.
In the 1992-93 game, Alan Grant and Ricky Watters each fumbled for San Francisco, and Dallas recovered both fumbles. Young also had a long touchdown pass to Rice called back for holding early in the game. Those three plays, in which Young himself did one thing very right and no things wrong, resulted in a 17-point swing in what became a 10-point game. Including rushing and sacks, Young produced 334 yards and 2 touchdowns on 46 plays (7.3 yards per play) against the NFL's #1 yardage defense and #5 scoring defense. He did have two interceptions, but the second came with the game out of reach after Aikman's famous pass to Alvin Harper and the ensuing touchdown. But unless Young could have overruled the holding call and demanded his teammates stop fumbling, it's hard to pin this loss on him--maybe he was supposed to gain 450 yards and 4 touchdowns against the league's top-ranked defense .
In the 1993-94 game, each team began the game with a touchdown drive. So far, so good, but then the NFL's 16th-ranked scoring defense allowed another long drive to make it 14-7 Dallas, and on the next possession, Young threw his only interception (the game's only turnover), a pass John Taylor got both hands on before it met Thomas Everett's arms. (The video is gone from YouTube, but it was an absolutely make-able catch that had no business becoming a turnover.) Dallas scored yet again, the 49ers punted, and Dallas drove for yet another TD to make it 28-7. One bad drive for Young (the punt) against the league's #2 scoring defense, and it was 28-7. Dallas would end the first half with 273 yards and 19 first downs. The 49ers never recovered. Even after Aikman left with a concussion in the second half, Bernie Kosar completed 5 of 9 passes for 83 yards and a score. It was that kind of game.
It would be pretty easy to write a similar narrative for Aikman's experience in the 1994-95 NFC Championship Game , but that only aids the more general point about the playoffs and how media and fans use it to judge quarterbacks. Yes, Young got worse statistically in the postseason, but so do most quarterbacks, including "winners" like Unitas and Brady. Yes, Young won "only" one Super Bowl on a series of great teams--of course, as shown above, they were great teams in large part because they had such a large advantage at quarterback, not to mention he won the one Super Bowl with possibly the best passing performance in that game's history .
Regardless, if you use wins and losses and ignore everything else, you are missing--intentionally--context and things the quarterback cannot control.
Of course, Young's teams were 8-6 in the playoffs (and averaged 34.6 points per game in the wins), including the 1996-97 playoff loss against Green Bay  when he threw 5 passes before getting hurt (and Elvis Grbac was hopeless in relief). Even if you only care about playoff wins, Young actually does just fine .
Speaking of Grbac, in three seasons with San Francisco (1994-96) he posted a 5.91 ANY/A on 446 pass plays, while Young put up a 7.08 mark on 1314 pass plays in the same time frame. With Kansas City, Grbac's ANY/A fell, but to just 5.67. Young's ANY/A was 20% better than Grbac's, while Grbac's Missouri ANY/A was 4% worse than his California ANY/A. Combined with Young's 1997 season, Grbac's numbers make it hard to claim that the supporting cast in San Francisco was the key reason for Young's success.
In a similar comparison from 1987-90, Young does well against Montana. Montana posted a 6.97 ANY/A on 1819 dropbacks in that time, with Young putting up a 7.34 mark on his 360 dropbacks. And, unsurprisingly, Young was the better rusher. He ran for just three fewer yards (662-659) on more yards per carry (6.2-4.1). With numbers that immediately compared favorably to Montana, it would seem that Young's problem in Tampa Bay was absolutely more his teammates than himself.
Young had a 3.53 ANY/A on 569 dropbacks with Tampa Bay, in 1985 and 1986. The eight-year veteran Steve DeBerg was their other quarterback, and he put up a 4.08 on 494 pass plays over both seasons. Despite Young's somewhat worse passing numbers, the Buccaneers were 3-16 when he started and 1-12 when DeBerg started, which was probably related to the fact that Young could run (658 yards on 5.8 per attempt) and DeBerg could not (30 yards on 11 attempts). Additionally, Young actually showed improvement in his second season, going from a 3.00 ANY/A to 3.73, numbers which track Aikman, who went from a 3.09 as a rookie to 3.88 in year 2. Nor were Young's struggles after arriving from a lesser league unique, as Warren Moon didn't get things going until his fourth NFL season. Young's two years in Tampa Bay should not detract too much from the rest of his career. Again, Young arguably outplayed Montana as soon as he joined the 49ers.
And Steve Young was, of course, a shoo-in Hall of Fame quarterback. Any criticisms of him are nitpicks, given the statistical dominance he displayed in the 1990's. To conclude, that chart I showed you earlier, with a little flourish:
If you weren't aware of just how good Steve Young was, maybe you are now.
 Montana first, then Manning, Brady, Marino, Favre, and Young. After that I see a large gap and face difficulty trying to rank Aikman, Elway, Kelly, Moon, etc.
 And a knack for spinning the ball in a weird way to confuse Jerry Rice.
 For more on Young's crazy efficiency, Brad Oremland's #8 ranking at www.footballperspective.com/guest-post-brad-oremlands-best-qbs-in-history-6-10
 Sporting News named him to their 1st Team in 1993, and UPI to their NFC (not NFL) 2nd Team in 1994 and 1995.
 T.O. became great, but it's hard to say a second-year third-round pick out of the Southern Conference who caught 35 passes as a rookie was already great. And besides, Young's #2 option in '97 was the immortal J.J. Stokes.
 It's usually pretty close, but here follow two examples. First, after the 1997 season, NFL Films ranked Aikman 10th and Young 11th on their list of 50 Greatest Quarterbacks. (Done so long ago that Ron Jaworski made the list.) Also, in 2010, NFL Network ranked Aikman 80th and Young 81st on their list of all time greatest players at any position. Of course, Football Perspective didn't have this issue.
 Or just not throw the first interception, you might say. So now we're turning one play in one game, out of thousands of plays and hundreds of games, into the difference in our ranking?
 Although Young's best play in that game, the TD pass to Rice to make it 31-14 at halftime, was a more difficult throw than Aikman's clincher to Harper two years prior, and did not rely on yards after the catch.
 Actually, that's another thing people complain about--that his opponent in the Super Bowl wasn't good enough. Supposedly, any quarterback could have produced 359 yards and 6 touchdowns against the 1994 Chargers.
 I often found that a debate about Young and Brett Favre would, at least before Favre ended up with a billion career starts, also come back to their head-to-head playoff record. But, as with Aikman, one game made the difference here. Green Bay went 3-1, but you can hardly count the game where Young and Favre combined for 87 passing yards.
 And you have to wonder, if Roger Craig does not fumble in the 1990-91 NFC Championship Game, does Young lead the 49ers to a win over the Bills in the Super Bowl? It's a total hypothetical, but it would be interesting to see how Young's legacy is impacted in the alternate universe where it happened.