Hmm... depends on your definition of core but i'd go
No More Heroes
Metroid Prime 3
Super Paper Mario
MLB Power Pros
Path of Radiance
Trauma Center New Blood
Mario Galaxy
Then for Casual... uh.
Carnival Games
Mario & Sonic
Edit: Oh... and Brawl... Mario Kart and Bloom Blox... which could fit either i guess. Can't believe i forgot brawl.