If you're going to play 3, and you own New Vegas as well (There's a Steam sale coming, they'll be going dirt cheap, most like), then I'd recommend looking into this: https://taleoftwowastelands.com/ - It lets you play FO3 through the New Vegas engine, which makes the entire experience a little more pleasant!
Aside from that, as many have said before this, Fallout 3 is a great place to start if you're looking forward to 4, but Fallout and Fallout 2 are great games in their own right, and definitely worth poking into. It's doubtful you'd need to know much, if anything from them, to get the most from 4 however.
Aside from that, as many have said before this, Fallout 3 is a great place to start if you're looking forward to 4, but Fallout and Fallout 2 are great games in their own right, and definitely worth poking into. It's doubtful you'd need to know much, if anything from them, to get the most from 4 however.