Updated: Added some commentary after engaging in some debate about some of the choices Based on a conversation on Facebook, I came up with this list, which, for now, will be presented with no further comment...
25. 2 Live Crew: While 2 Live Crew's lyrics were mostly inane and pointless, they had three very, very dope MCs and Mr. Mixx is one of the top two or three DJs of all time. Go back and listen to any of the MegaMixx tracks (they did one on each album) and they hold up very well. And no matter which song it was, or how dumb the lyrics were, every song sounded tight.
24. Doug E. Fresh
23. Snoop Dogg
22. A Tribe Called Quest (& Q-Tip)
20. Kurtis Blow
19. Wu Tang Clan (& Method Man, ODB, RZA)
17. Will Smith/DJ Jazzy Jeff & Fresh Prince: I know everybody clowns on Will Smith, but he was one of the most technically proficient rappers ever. Go back and listen to "Boom Shake the Room," "Then She Bit Me," or anything off "He's the DJ, I'm the Rapper," and you'll find that his songs are really difficult to do and they are almost all perfect and he certainly has one of the all-time great personalities in any art form. And if you don't think his stuff is hard, go try "Parents Just Don't Understand" or "Boom," and see if you can pull it off. I've performed both of them and they are hard as hell and I've never seen anyone else pull them off well
16. Eric B & Rakim
14. Biz Markie
13. De La Soul
12. 2 Pac
11. Outkast (& Big Boi)
10. The Coup: The Coup's album from late 2012 is one of the best albums of all time, regardless of genre
9. Digital Underground: I love Digital Underground. Everybody knows them as a one- or two-hit wonder, but their first 3-4 albums were all amazing
8. Run DMC (& Rev Run)
7. LL Cool J
5. Kanye West
3. NWA (& Ice Cube, Dr. Dre, Eazy-E)
2. Beastie Boys
1. Public Enemy
Honorable mention: Afrika Bambaataa, Afroman, Biggie Smalls, Childish Gambino, Common, Cypress Hill, EPMD, Fugees (& Lauryn Hill, Wyclef), Grandmaster Flash (& Furious Five), Ice-T, MC Lyte, Missy Elliott, Naughty By Nature, Redman, Slick Rick
Someone asked why no Sugar Hill Gang. Here's why: The have a few good songs, but that's about it. Plus if you read the story of how they were put together (totally artificial to capitalize on the new rap "craze") and how they didn't put in any of the work building up the art form and took credit for the work of dozens of better artists who blazed the path for them, you get kind of a bad taste in your mouth. They are basically a prefab group like the Monkees and while they did have a few great songs, they only had a few and their only influence was that they were the first to get played on the radio, but that was going to happen anyway, without them.