They were all very good. My favorite levels are (in no particular order)
*DS trench from SSW
*Hoth battle from SESB
*DS battle in Falcon gun turret
*DS attack run SROTJ
*Duals with Darth Vader in SESB & SROTJ
I hated the way they did force powers in those games though. I wish they had done it where force power regenerates (like in the DF/JK series for pc) rather than having to keep getting force powerups.
I also wish they had had a playable dual between Obi Wan and Darth Vader in SSW