A video game responsible for many sleepless nights?

With all this talk of movies, music and books, I’m curious to know what video games have been an addiction for you either presently or in the past.
Back in the day, I was pretty addicted to Super Mario World and Diddy’s Kong Quest.
I also really enjoyed Crash Bandicoot and Pac Man World 2.
And how could I forget Spyro. :)
I’ve always liked playing the real ‘cutesy’ games with little animals and silly bosses that you had to kill in order to get to the next world.

However, for the last couple of years, Grand Theft Auto (mostly San Andreas) has been responsible for the majority of my all-nighters.
I can’t get enough of that game.
Strategic/time management games pull me in as well. I really enjoy The Sims, The Movies and Roller Coaster Tycoon.

Which has it been for you and what in your opinion draws you into this particular game and is responsible for the addiction?
Have you ever put off doing important tasks because you simply couldn’t back away from the game?