IMO the top 3 should be Uncharted2, Little Big Planet and MGS.
But being IGN they would most likely put one PS3 exclusive and place two multiplat games in the top three.
Actually being IGN they may very well put all multiplat games in the top three to make out that the best games on PS3 are available elsewhere, as most anti-PS3 people will probably agree.
Maybe I am being cynical but it wouldn't suprise me if this turned out to be the case.