Been playing my old PS2 games again and I've got to say:
SSX3
This game just won't age.
Started a new save file and completed Conquer the Mountain with only Platinum Medals just a few hours ago (excluding the Freeride medals). Amazing soundtrack. Outstanding track design and gameplay. Crap loads of content.
Out of the more recently released games that I've played:
Donkey Kong Country: Tropical Freeze
Pure platforming bliss.