Threads like this are funny. Take a QB. who was somewhat disappointing and find another who took a little while to shine.
Then posit that your QB might do the same. Might happen.
Let's not think about all of the QBs. that initially disappointed that went on to become busts, which is the far more common result.
Manuel might become great, but as of now that is sort of a long shot.
I don't like how many injuries he already has had, one of which was from a stupid play of his. I am also not fond of his throwing motion. This does not mean he will not have a good career, but cherry-picking another QB and extrapolating from there means zero.