About 10k hours went on Counter-Strike 1.6 alone. Dozens of mods, thousands of servers, lot's of fun, about just as much frustration. Been a part of various CS communities, and some of them felt like a second family at the time, like some may feel about SS.
And about one-third of that amount of time went on TES 2-5 games: Skyrim, Oblivion, Morrowind and Daggerfall. I don't think this this series requires introduction. TES games are good enough as they are but the colossal effort the modding community has put into customizing the base game is what makes them great. People are developing mods for themselves and others (not primarily for money like big gaming industries), and probably because of that they want to make good mods.
I really like Vampire The Masquerade: Bloodlines. Around 25 playthroughs in total. Funny dialogues. Playing as a badass vampire. One of the few games where I really liked the gameplay even though it wasn't very challenging. There are a two clans that allow for a quite unique playthrough. (Malkavian, Nosferatu.) I wouldn't recommend them for the first one though. I liked the leveling system. Instead of earning XP from murdering everything on sight, you get it from doing quests, so there's no pressure to start a massacre. (Still doable though.)
I also liked KotOR 2 The Sith Lords. The dialogues are written very thoughtfully, and there are lots of philosophy stuff. Kreia and HK are probably one of my most favorite characters in video games. When I was a kid I liked this game purely from gameplay perspective, mostly I couldn't understand what they were talking about.
OK, I think I should stop here somewhere.