Fallout is Single player FPS-TPS, RPG series with heavy emphasis on exploring, adventures, learning skills and killing bad guys with big guns. Its the kind of game where you can lose long hours just wandering around doing stuff or having fun. The best part is you can pick up any Fallout game and it will still be fresh for you. A LOT to do in the game.
I would highly recommend playing in sequence. Forget the first two, start with FALLOUT 3, its an easy game to play. Just expanded, way too much to do, way too much to explore and way too much of everything in a perfect open world setting. Hell, watch some youtube videos and get the feel of it.