In regards to FPS- Seldom do I actively play in First Person. I prefer third person, as I like to see my character when I play. The scenery wont magically change to crap the moment I go to third person.
As for what I like better, it depends. I enjoy that nostalgic charm that Fallout and Fallout 2 has. Fallout and Fallout 2 have great dialogue, but Fallout 2 get's a bit tiring with it's 'LOL THIS DIALOGUE IS BREAKING THE FOURTH WALL/BLATENT MOVIE REFERENCE, DID YOU GET IT? HUH? DIDJA?'. 3 and New Vegas were fun visually, but New Vegas hit the story and dialogue better. As for 3, I prefer Fallout 3's retro-futuristic 1950's Atomic Family optimism. And GNR will always have a special spot in my heart.
Edit: @ F+N=O, another thing you have to take into consideration, the combat crosshair wise in Third Person is wonky in 3 and NV. I only use FPS for combat or cutscenes because those are the best moments for them.