I really enjoy Metroid Prime 2, actually. I'd almost go as far to say that I enjoy it more than Metroid Prime 1. I used to really hate it, though, and now I can't remember why I did. Maybe it was that darned Boost Ball guardian. >_>
(My Metroid Zero Mission save battery actually isn't dead. I turned it on this morning and saw that my save files have returned to me, and I don't get how it did.)