Fallout 3
Could never get into the 2D ones, the color scheme of them kind of hurts my eyes and gives me a headache. Fallout 2's story sounds really compelling, which bums me out that I can't visually handle it. Fallout 3 is inferior in game mechanics compared to both New Vegas and 4, but story wise is the most solid of them all, which is why it's my favorite. Nothing about the New Vegas story line compelling at all. 4 has some great ideas, but doesn't follow through on most of them and just left me annoyed with a lot of important unanswered questions. The "twist", which I guessed was going to happen, was the only enjoyable part, the ending afterwards was frustrating. Hopefully one of the DLC's will continue the after the end of the game and answer the questions that are buzzing in my head. Also nothing you do really has an effect on the world, a problem that's getting worse for Bethesdas games in general.