Wind Waker: A Zelda game. Combines action and adventure, puzzle solving, etc.
Skies of Arcadia: Japanese console RPG. You know the deal. Run around in dungeons, fight off random encounters in turn based combat, talk to NPCs, solve puzzles, etc. Not much action in there, but a pretty lengthy plot.
Final Fantasy Crystal Chronicles: Multiplayer Hack&Slash RPG. Run around (alone or with friends), kill monsters, kill boss, repeat. Requires one GBA per player in multiplayer, singleplayer can be played with a standard controller. IMO the art style goes into the same direction as Wind Waker, though rendered differently. If you want action, get WW first, if you want an RPG Skies is the better choice.
Harvest Moon: One of those eco sims. You know, the kind where you start out poor with bad equipment and have to work for hours to get some money together. Involves a lot of repetitive cores (well, it IS a job simulation after all...)
Personally I liked WW, loved Skies, tolerated FFCC and hated Harvest Moon, but your oppinion on the subject might greatly differ.
Besides I want to lobby congress to make it a crime to own a GC but not Viewtiful Joe. Seriously, Joe is one of the best games this system/generation has to offer. Most would recommend WW first, I'd say go for Joe.