So I added up my playtime between all my characters, it came out to be 16,000+ hours. I'd estimate about 20% of that is idle or accidentally leaving it on overnight etc. There's a book that says 10,000 hours masters a task or skill. I'm sure that's debatable.
Next highest game is Team Fortress 2 with a little over 1,000 hours. Left 4 Dead 2 about 850 hours. I also played the bajesus out of Counter Strike 1.6 but don't have hours on that.
I'm not sure how I feel about this.