What game have you spent the most hours playing?

I've spend the most hours playing in the game "Sims". I started playing from the very first Sims and now it's fourth part already.
My favorite part was Sims 3, it had many options and the best one is to walk all over the city without downloading window. It also had option to look for different things all over the city, such as flowers, stones, insects, etc.
Most of all I like to build house and design everything inside it. Of course, it's interesting when you're using cheats. But it's not so interesting to use cheats when you're playing because there is no need to work, if you have so much money and whole the best furniture you can buy in the game.
So, I like to build with cheats but play witout cheats.
Anyway, I don't have too much time now for playing, that's sad.

Let me know, what game have you spent the most hours playing?