Starcraft > D2. I was pretty addicted to D2 for quite the long time, but I couldn't go back and play it now. If I wanted, I know I could find a friend to go and play starcraft with me right now, it just never gets old.
Starcraft wins, IMO. I was hopelessly addicted to that game; I played it from when I was 9 to about 14/15. Every once in a blue moon I'll play a game or two and realize how good of a game it truly was.
I'd say the game that robbed the most hours away from my life would be D2. That game was at one point like crack, it was all about when I got to play it next. Starcraft has and always will be a fun game, seeing as it's the very first computer game i've ever played. Warcraft has never really been a big thing for me until the release of WoW.