This is not even close.
Luck is the best prospect since Manning.
RG3 is not even the best spread-running dual threat QB in the last 12 months.
Luck is not over-hyped. RG3 is getting into over-hyped category when he is compared to Luck.
There is absolutely 0 indication that RG3 can run a pro-style offense. There is a long history of spread college-dominant QBs who fail in the NFL. This doesn't guarantee that RG3 will fail, but the absence of evidence of him being good in a pro style offense makes him significantly less of a prospect than Luck.
Answer me this: as a passer who has to run a pro style offense, what does RG3 have on Case Keenum as a passer? The answer is nothing. They both ran gimmick offense, but Case put up better numbers.
The thing that gets people excited about RG3 is purely his dual threat running ability. And that simply is not what wins in the NFL. History proves this. If it was, Vick would be the greatest ever as he was a FAR better prospect than RG3 is.