Tupac is good for bass. I don't like my bass to be overbearing - just clean and healthy. I find that a lot of rap has too much distortion. Here's some non-rap tunes I like for clean, healthy bass:
Puddle of Mudd - Blurry
No Doubt - It's My Life
Wheatus - Teenage Dirtbag
Hoobastank - The Reason
Metallica's black album has some pretty good bass tunes too.