I've charted the height and weight, runs, rushing yards, touchdowns and interceptions per game and rating over the career of the players in their Scouts, Inc ranking order (and attempted to remove stats that came from mopup duty when the player was a backup):
A squint at the table reveals that there's a pretty even smear of heights across the rankings. I would consider the top 6 in this table to be the elite quarterbacks of the NFL, and 2 of them are short enough that draftniks would be waving a red flag around them. Both of them dropped in the draft. It's tricky to play the numbers games with whether being shorter actually leads to a higher failure rate (teams may avoid shorter players unless they are otherwise really good prospects ...), we can agree that being under the prototypical 6'4 mark is not a clear indicator of professional failure. Recently retired quarterbacks Kurt Warner and Brett Favre were also 6'2, and Donovan McNabb was also one of the better quarterbacks in the league until the last few years.
Only one of the elite QBs, Rodgers, actually gains significant yards with his feet, the rest who rush for over 10 yards per game are clustered right in the middle of the pack. Rodgers is also the most effective passer in the league. What really separates the top quarterbacks from the rest is their pure passer rating (all career 91.7 or higher) and decision making. 4 of the elite have TD:Int ratios over 2, all are better than 1.67. The vast majority of the rest are under a 1.5 ratio and mid-80s rating. The top quarterbacks make plays with their arms and brains, not their feet.
It remains a mystery why teams use high draft picks on players who didn't demonstrate sustained success in passing the ball. There's a reason for the 26-27-60 and Bill Parcells rules. They ensure that quarterback draft prospects pass the smell test. I haven't inspected draft picks' success with respect to these rules, but my general sense is that failing them does indeed predict NFL failure.
Generally speaking, project quarterbacks don't turn out well. The list is long, and most of these highly drafted players don't currently project well:
2011 (preseason games only so far)
Cam Newton: 5.3 ypa on 40% passing
Blaine Gabbert: 4.6 ypa on 51% passing
Jake Locker: 6.1 ypa on 54% passing, 1 TD, 1 INT
Tim Tebow*: recently demoted to 3rd string
* - passes all the rules, but serious red flags around length of delivery
Matthew Stafford: promising but has missed a lot of time to injury
Joe Flacco: has taken the Ravens to 3 straight playoffs
Josh Freeman: projecting as franchise QB for the Buccaneers
Jamarcus Russell: out of football
Brady Quinn: couldn't beat out Derek Anderson in Cleveland, backup with Denver
Vince Young: promising player, but couldn't seem to get it together mentally
Jay Cutler: traded to Bears due to personality, leads the NFL in interceptions over the last 2 years
Alex Smith: Getting his 4th fresh start with the 49ers
Aaron Rodgers: Well on his way to meeting the requirements, but left a year early. Is one of the best QBs in the NFL
Missing from the list are the players who passed the smell test:
Sam Bradford: solid rookie year, promising future
Matt Ryan: established himself as Falcons' franchise QB
Matt Leinart: fizzled out in Arizona, now dink 'n dunking in Houston
Depending on which group Rodgers falls into and not including the 2011 picks, the 1st round players who pass the smell test as passers have a 67 or 75 percent success rate compared to a 40 or 33 percent success rate for those who didn't. In other words, the smell test accounts for a doubling of the success rate in drafting quarterbacks. The comparison goes to a factor of 3 if you believe me that none of this year's top picks will become franchise QBs.
Why, oh why, do teams keep thinking they are smarter than common wisdom?