Manning is a 2-4 year deal at QB then we're back to where we were before we got him, namely trying to find a franchise QB.
Having a quality QB is just too important to pick anywhere else IMO, and of the elite guys in the league Rodgers is the youngest. You're pretty much a guaranteed contender every year for the next decade with him.
If you exclude QB's then it becomes a bit more interesting.
Jason Pierre Paul, JJ Watt, Patrick Peterson, Patrick Willis and Calvin Johnson are the five that come to mind quickest to me.
I'd probably go with Peterson, what an heir he'd be to Champ.