Mario Party 4 5 and 6 are all good! I dunno about must own but they're fun times.
yeah not a good list though. some notable omissions, and some junk there instead.
SSBM
Twilight Princess
Wind Waker
Timesplitters Future Perfect
Resident Evil 4
Metroid Prime
F-Zero GX
Prince of Persia Sands of Time
Tales of Symphonia
Mario Party 6
that seems like a better list. a little tough, though! I'm not sure the Gamecube actually has 10 "must play" games. 4 or 5, maybe. Take away multiplatform games and it's less than that.