I figured the OP meant the whole Fallout series, but it doesn't matter. It's the same answer.
Do I want to wander from one end of the wasteland to the other, smashing heads when necessary? Well, maybe. Do I want to complete interesting quests that mix brawn and brains, given to me by shady and interesting people? I suppose it couldn't hurt. Do I want to try to survive in a harsh environment? If I have no other choice... Do I want to build the backstory, appearance, personality and skills of a person and then set them loose in an interesting world? HELL YES WHERE DO I SIGN oh I only need to put in the disc okay
See, the Fallout games provide a wonderful template for me to create in. I don't put myself in my character's shoes (use my own name? How boring!), I decide what kind of person they are and set them loose, making decisions in every interaction as to what I think they would do. Everything from their skills to their choice of clothing helps reinforce who I think they are.
Whether it's a clever, cowardly sniper, a misanthropic "mad bomber", or a sledgehammer scientist-messiah, Fallout has enough weird and extreme situations for me to bounce my characters off of. It has nothing to do with an obsession with violence or bloodshed or anything like that. Even the best FPS's just don't float my boat. It's all about creation and control of the virtual world. I am a red-blooded male and the occasional monster beatdown that has no moral consequences certainly doesn't lessen the game's impact for me... but it's NOT why I play.
I'm not a violent person. Some of my characters are, though.