Battalion Wars 2 would have been a great game had they not taken out 4 Player online CTF mode.
Without that I'd say its a good rental.
If you bought it and looking to trade it in... Metal of Honor:Heros 2 would be the next choice.
MOHH2 has 32 player online servers with no Friend codes. Simply type in the persons alias and save it. Then you can see when they're online, jump in game with them, etc.
MOHH2 is what Wii's online should be.
Mario Galaxy is fun... but extremely easy. Plus they erase all your 1ups on a reset, so it makes exploring all the planets a waste of time. There is only a couple good maps anyway. Galaxy would be a good rental from Blockbuster. Rent it for 3 weeks, beat it, return it. Its a fun game but gets old. The resetting lives thing blew it for me. Why work hard when a reset will take it all away?