Some great drummers off the top of my head:
Ginger Baker (Cream, etc.)
Dennis Chambers
Carter Beauford (DMB)
Dave Weckl (Chick Corea, solo)
Neil Peart
(Rush)
Martin Lopez (Opeth)
Art Blakey
Buddy Rich
Danny Carey (Tool)
Mike Mangini (Steve Vai)
Steve Gadd (solo, Steely Dan - listen to the song Aja for the love of God)
Dave Lombardo (Slayer)
Elvin Jones (Coltrane's band, etc.)
John Bonham (Led Zeppelin)
Stewart Copeland (The Police, Oysterhead, etc.)
Mike Portnoy (Dream Theater)
Gene Krupa
Keith Moon (The Who)
Terry Bozzio
Carmine Appice
Steve Smith
Freddie Gruber
Ian Paice
EDIT: Almost forgot to add Jordan Burns of Strung Out (he's probably the most well-rounded and talented drummer in punk)
I can't choose a favorite since comparing different musical styles is futile. On an overall technical level, Dave Weckl or Dennis Chambers is probably the "best," but they wouldn't exist if Elvin Jones and Buddy Rich hadn't broken some ground. While Neil Peart is a great rock drummer, his lyrics impress me more than his percussion nowadays. Martin Lopez and Danny Carey are my choices for top rock drummers these days. Stewart Copeland's formidable hi-hat work and Steve Gadd's inventive playing also make them tough contenders. Mike Mangini is frighteningly ambidextrous and Carter Beauford is quite simply unbelievable at times. I'm sure there are plenty more amazing drummers that I neglected but I'm tired and hungry.
It's all about the groove and the pocket!