I know Manning hasn't been good for the first half of this year.
In general though, if you had to pick a QB to build a team around for the next 5 to 10 years, I think he would be near the top of the list.

Who else has been good year after year in this league?

Brady
Brees
Rivers
Rothlisberger
McNabb

Maybe Cutler will be good and Eli Manning has had 1.5 good years right now.

I think that's about it. Rest of the QBs are either mediocre or just plain bad.