i'd say Monster Hunter Freedom 2. i put in 300 hours on that game before i put it down. also i believe Capcom is releasing Monster Hunter Freedom Unite in the future.
Get Patapon, don't even think about it, just get it.
Most unique game I'd played in some time, great art style, etc etc etc. It even had a great story. Plus it's cheap.
I'll second the vote for Crush, too. Definitely an under-appreciated gem. Very unique, very challenging, very fun. The art direction blows though. But that's just a nitpick.