Dragons Age: Origins or M Effect 2?

DA is definitely longer and has a much richer story and characters. You are looking at 50-60 hours of game play if you are thorough. The only things ME2 really does better is graphics and combat. I also don't think you would enjoy ME2 as much without playing the first one. I played them out of order and I had to constantly go look things up to figure out what was going on. Considering that your choices carry through the whole series it's best to start at the beginning.