You say he can be a great QB and then say he can be a sane Vince Young? Vince Young went crazy after he was benched. He also wasn't even average before that, let alone great. Hell, he was basically awful his entire professional career. So he's really a great comparison for Tim Tebow.
2006 per game averages:
Passing: 146.6 yards on 51.5%, 0.8 TDs, 0.9 INTS, 1.7 sacks, 66.7 QB rating
Rushing: 36.8 yards, 0.5 TDs, 0.8 FUM
2007 per game average:
Passing: 169.7 yards on 62.3%, 0.6 TDs, 1.1 INTS, 1.7 sacks, 71.1 QB rating
Rushing: 26.3 yards, 0.2 TDs, 0.7 FUM
In the two best NFL seasons of Simple Vince's career, he accounted for 189.7 yards of offense per game, 21 passing TDs, 10 rushing TDs, 30 INTs, and 22 fumbles. 31 total TDs. 52 total turnovers.
Even I think Tim Tebow can do better than that. If that makes him great, then I'm at a loss for words.
They were both unbelieveable college football players. Two of the greatest of all time. But college success and professional success are two entirely different animals.