This is a tough question and one I know a lot about. While I cannot answer your question, there are just too many greats, I can give you a couple of great people to find some trackers of.
In no particular order (stand ups)
1. Bill Cosby - If you can manage to put what he's done criminally - Cosby was an all time great and Cosby Himself maybe the greatest stand-up album put to vinyl.
2. George Carlin - His oldest stuff is his best. - RIP
3. Patrice O'Neal - RIP
4. Bernie Mack - RIP
5. Woody Allen - He's got some old stand-up that's great, but a little hard to find.
6. Richard Pryor - RIP (Considered the best by the best) That N-----r's Crazy was the comedy record that changed comedy records
7. Bob Newhart - slow, intentionally stumbling, and wholesome style, don't let his great works be forgotten.
8. Steven Wright - deadpan one liners lulling out of a comedian with a pulse of about 7 beats per minute
9. Mitch Hedberg - IMO, could have been one of the top 10 of all time, but he couldn't put down the needle.
10. George Burns - Say goodnight, Gracie
11. Dave Chappelle - Voice of a generation
12. Richard Lewis - A Jewish comedian from NY/NJ who uses self-deprecating humor and has hundreds of neuroses? It may not sound original, but he's great at it.
13. Lewis Black -
These are just a few of my top peeps.
I haven't downloaded yet myself, but if you want to get a good sampling of stand-up, I hear this is a good file to DL.
Stand Up Comedy Pack [Torrentleech org]