Poor, for several reasons.
I played through it a few times, only to be hopeleslly disapointed. The game was obviously relying on the hype of the movie, and hoping to shock fans with the bits of the movie they showed. This, of course ruined the game. I was nine when this game came out, and I beat it in a week. So don't expect any great challenge.
I was overall disapointed. This game isn't even worth a bargin bin buy-out, if you asked me. I enjoyed the Co-Op missions with my brother, as Co-Op missions were, at the time of the game's release, hard to find.
A few awesome lighsaber moments, but other than that, the game offers very little enjoyment. All star wars games are either great, ir poorly made. This game falls into the second group.
Sloppy controls, poor gameplay, weak and confusing story, and poorly made missions cannot be saved by lightsabers and blasters.
Not a very good game by any standards, and I would recomend against buying it. It will offfer very little entertainment, and will only frustrate you. You'd be better off without
Star Wars Episode III: Revenge of the Sith
Watch the movie instead.