I heard that Mario Kart Wii is only so-so. Super Mario Galaxy, according to more hardcore gamers, was too easy (probably since they thought fully completing Super Mario Sunshine was so hard). But I thought it was awesome, so I would recommend it first. Especially if you're a fan of SMB 3. I haven't played Super Paper Mario yet.
Haven't heard a lot about TWEWY and FFTA2, but I've been meaning to get the latter.