I think it is kinda cool how we can actually track game time now. Not like before then, when we can only really guess. Aside from D2, another one I put in a lot of time is Quake 3. I still play that every now and then.
According to steam, I have played 3 games over 100 hours. Here is my top 5.
313 hours: Fallout New Vegas
246 hours: Skyrim
245 hours: Civilization V
26 hours: Deus Ex: Human Revolution
26 hours: The Sims 3