The 2 Games I Couldn't Put Down

Of all the games I ever played, only 2 comes to mind that I actually couldn't put down until they were completed. Those were:

• Mario Galaxy - I had purchased Mario Galaxy on a 4 day weekend thinking that it would be something to do and it sure was. My girlfriend of the time, who wasn't a gamer, and I spent the entire weekend, non-stop, playing it. When I needed a break, I took a nap but she continued on and we completed the game in roughly 40 hours straight. To this day, it's still the best Mario game I ever played.
• Mass Effect - Mass Effect had be out for a while and I had read raving reviews about it. I remember it being on special, on a Friday night, on steam. I purchased it and from the first minute on I was immediately captivated by it. It took me roughly 25 hours to beat and I did so in one sitting. While I enjoyed the series overall, only the first game of the series managed to literally keep me up at night.

I have since played many other games, some of which I spent way more hours on, but those are the only 2 games that managed to grab me from the minute I pressed "play" to the end credit with barely any breaks in-between. 

Sometime I wonder if I'll ever find a game that'll give me the same rush as those 2 and if I find one would I even have the energy to complete it in one sitting?

What are the games that you weren't able to put down?