Fallout 3 is incredible. And to be frank, its more realistic if you haven't played any of the other games, because you don't know anything about any of the organizations and are free to make your own, uninfluenced opinions on the basis of what your character knows, which since you haven't played through the other games, is also the extent of what YOU know. If you are going to play it, do yourself a favor and also install the Fallout 3 Unoffical Patch, which fixes an amazing amount of bugs