as for star wars games, i found rogue squadron 3 to be a pretty good mix, driving, flying, walking. very well balanced in terms of those 3.
as for action rpg...can't go wrong with zelda.
haven't really played any racing games on the cube, but I'm sure you can do alot worse than F-Zero.
on a side not, I would go and grab ssx3, it been awesome for the first two. although i've heard it said that the GC version is the weakest, due to there not being enough buttons on the Cube controller.