The Tebow discussion is an interesting one in terms of how great "great" really is. I don't think there can ever be a "Greatest of All-Time" (except for the player that makes Gary Danielson change his underwear the most times during a game, Tebow has that one locked down), given the differences in eras, and competition levels, and equipment, and any number of other things.
That said, players who are considered to be among the greatest of all time are usually only truly thought of that way as time passes. Example: I saw two really fucking good running backs at Oklahoma State in my lifetime. But Thurman Thomas is remembered as a very, very good college player who went on to have an NFL HOF career. Worthy praise, but he isn't nearly on par with Barry Sanders, who along with being remembered as one of the greatest NFL players of all-time is remembered as one of the greatest collegiate players of all-time. Colt McCoy will go down as one of the great Texas QBs, one of the great players of the "oughts", and still has a chance at a Heisman. However, he will not, I don't think, ever be in the same discussion as Vince Young, who didn't win a Heisman but is considered one of the great college QBs of all-time.
Point being the jury is still out on Tebow's full place in history, despite what the outright haters and the media masturbators would have you believe. He's won a Heisman...then again, Gino Torretta and Andre Ware did that. He's won a NC, but then again Krentzel did that, and although I love him by God for it, he isn't Vince Young. And Schaeffer only completed 6 passes for Penn State in 1986 too. He's won a Heisman AND a NC, but then again Eric Crouch did that, and he isn't exactly filling out the rosters of all-time teams. My opinion is that Tebow has proven himself to be WAY better than those players already, but my point is there isn't a specific accomplishment, or a combination thereof, that one can point to and say he's the GOAT. But make no mistake about it, if his senior year goes the way it looks like it will, he will be in the conversation with Sanders and Archie and Vince Young and the rest...and he will belong there. But I don't think he does just yet.