Mario 64. I mean... this game does have nostalgic interference... as it was the first 3D game I ever played. But I play it every year or two still. I love the level designs.
Super Mario World, and Super Mario Bros are my next favorites. Followed by Earthworm Jim
I enjoy ratchet and clank, jak and daxter and little big planet... and all the new marios after 64 but don't really love them.