In all honesty, if you are only going to ever get one of them, I would say Dragon Age. I'm about 40 hours into it, and almost done the main story, but there is still so much more that I want to do. I can see 100 hours coming out of it by the end. Demon's Souls is an amazing game itself, but after about 60 hours of playtime and NG+, I'm feeling a little burned out, and I don't really want to do a NG++ so I may be done with the game for awhile. I would highly recommend getting both though, as they offer amazing experiences.