If you're talking debuting 2000 and After
Then,
Lupe Fiasco - Premier lyricist in this group, imo
Kendrick Lamar - Always well written and thoughtful, I know the opinion on him is severely divided, but he's put out some of the best music of the past 15 years.
Drake - I know this site hates Drake, and I wasn't the biggest fan of his past 3 albums, but he is here off of impact if not off the strength of his music.
Royce Da 5'9 - One of the dopest spittas of all time, and he does so at a very high level. He's only had some commercial success but he is an amazing rapper and once
Rick Ross - He is arguably the modern day stand in for Biggie, a lot of street appeal and enough commercial success to stay around as a force in music
Wale - This may be a surprise to some but he is one of the most well balance rappers out, he can regular dude rap, conscious, slow jams, anything, and has carved out a nice career for himself. His last album was one of the freshest things I've heard in a while
Game - One of the most consistent West Coast MCs despite the name dropping, has dropped 2 near classic albums.
Kanye West (despite not really liking his last 2 albums)
Nicki Minaj - I hate all her albums but I'd be lying to myself if she hasn't proven herself to be the most talented female MC out moreso since she seems have gone back to making straight up hip-hop
Killer Mike - I would say is a combo of Ice Cube and Willie D, but he has consistently dropped heat since leaving the Dungeon Family