Mass Effect 3 was really good (I have a PS3, so I can't speak for the other two). But not as good as Fallout at all. ME has the same "alter the story" stuff, but not nearly as much free roam or exploration. It was basically "choose which planet you'll have a quasi-on-rails repetitive FPS level on." Great game, still I by far prefer Fallout. One suggestion: get Skyrim over Mass Effect anytime ever. ME3 had a ton
of innuendo/sex stuff and partial nudity and... stuff. I played it in my room.
EDIT: And to be honest, I thought the bad guys in ME3 were boring. Again, though, I have a PS3, so I can't speak for the other two.
EDIT AGAIN: ME3 had limb splatter, too. Heads explode often if you aim right.
I'm actually replaying New Vegas now. I just got Boone as a companion for the first time. Suh-weet. I think I'll go for NCR this play-through. I played through once and became Dictator of Vegas, and another time I didn't complete the play-through, but had been going for Caesar.