AP should be the MVP and it isn't even a debate, IMO. What these guys did last season should have no bearing whatsoever on the MVP award. What their teams did last season with or without them should, and how their teams would fair this season without them definitely should.
The Vikings without AP are nothing. Especially since Harvin was put on IR around week 11 or 12 I think? The Broncos could have gotten another decent QB or stuck with Tebow and probably still would have won the AFC West considering how bad that division is, but the Vikings without AP are down there with the Lions in that division.
Not to mention what Manning is doing really doesn't impress me and shouldn't impress anyone. I think everyone saw this coming if he was healthy, he's playing at an elite level along with a few other quarterbacks. I don't think anybody saw AP doing this, he's separated himself from every HB in the league and it really isn't close. Not only that but he's cemented himself as one of the best running backs of all time. What he's done this season is just so rare and unexpected, that's why I give him the nod.