The gap in quality isn't quite so severe that you can't take a step back, and you won't run into the problem where you get to the first 'real' mission 3 bloody hours in and put it down for 8 months. Like, I know it isn't an EXACT parallel, since an 8 hour campaign isn't the same as a 50+ hour one, but every time somebody says 'you should play Fallout 3 before you play New Vegas, because you won't be able to go back!' the end result is always that they never play New Vegas because they get burned out on a way worse game.
This is the kind of logic that gets people burned out on the game before they get to the good one though. If you enjoy one of these, you'll likely enjoy them all, so just play all 3 in order. I also don't see why you'd want to miss any of the stories. Originally posted by Drain:Play them in order because you want to go up in quality, not down.