Kurtis beat me to the punch, but here’s my take.
Some games you quickly play through and get tired of. The Diablo series has not been one of those games. Diablo was one of the first RPGs I played on the PC. Diablo II saw many, many, many hours spent playing with friends on Battle.net, probably more than Starcraft and Warcraft combined.
Blizzard just announced Diablo III, go watch the gameplay video and start drooling.