Hotel Dusk and Elite Beat Agents if you don't have it already.

Hotel Dusk is like Phoenix Wright, but it's different (better? waiting for my game to get to me...). Metroid and Starfox are ok, but if you can *only* buy 2 games, they should be quite a bit lower on your list.

My top 2 reccomendations would be Elite Beat Agents and Hotel Dusk, but other high-ranking choices:

Castlevania x2
Phoenix Wright x2