Both games are potential time sinks, but in reality you get bored after a while. There are lots of games that can potentially ruin your sleep hours. For me, the champion in this is Silent Hunter 3 which I played for 37 hours straight. What I saw the sunrise creep through the window and looked at the clock, it took me a few minutes to figure out what PM meant (it was actually the sunset, on the following day... yeap).
But over time you get bored with almost every game. Except one. One that is the most addictive game ever made. One that will rob even a casual gamer hundreds upon hundreds of hours per year. Year after year. World of Warcraft will never, ever be beat. Since there are millions of players in this world, at an average of 2 hours of play per day per player (which is a huge underestimation), this game eats up the total life span of about 28 lives of an average of 81 years EVERY DAY.
I wasted 3 years of my life with it and I can't believe just how dumb I've been. Most of my friends still play it, day by day, 7 years and going strong.