Since you bought a Wii to begin with and you really seem to like Strikers, I'm going to assume that stuff like Call of Duty isn't really your thing. Zelda: Twilight Princess is a great title, as is Super Mario Galaxy. Metroid Other M is good too, if you like cheesy voice acting and overwritten dialogue.
The best thing about the Wii by a long shot is the virtual console. Pretty much any game you remember playing while you were growing up (NES, SNES, Sega, and more) is there, and the prices are good too.
