in reality, ANY player can be a first-round pick. if they have an absolutely outstanding senior/junior season, then they might be looked at as the best at their position for that season and be highly sought-after. but the only thing that is absolute about that is it's a possibility. there's no guarantee....it's only possible. and no matter how possible it is, it's the probability that needs to be looked at.
sure he looks good, now. but how will he look when the bodies start hitting and pads start popping? full speed in practice is WAY different than game speed. he may very well be good...even great. he may very well go down as the best quarterback to come out of uga and break all the records there. but will there anybody better? maybe.
good in high school doesn't guarantee good in college
good in college doesn't guarantee good in the pros
bret favre was a pretty decent college qb that nobody really looked at when he played for southern miss. but the day he lit up the TIDE sure opened some eyes. and then he goes on to have a great career in the pros. and the same could probably be said about tom brady. he wasn't really looked at as all that good in college. sure he had some solid games, but he didn't stand out as the best. even in the pros, he was behind a pretty decent qbk...until that guy got injured. after that, he accomplished a lot more than probably any other qb.
the florida qb from the '92 team, shane matthews, spent 14 years in the nfl. he was regarded as one of the best in college (certainly in the SEC) at that time. but when he got to the nfl, he spent almost his entire career as either the backup or the 3rd string qb. he did start a few games for a couple teams, but was never the same qb that he was in college. still, 14 years is a helluva career in the pros. and i'm sure he made a decent amount of money while not doing a while lot.
so being good/great in college doesn't necessarily equate to being good/great in the pros. also, being mediocre in college doesn't mean you won't be one of the best ever in the pros.