This is hard. I played Fallout 1 and 2 first... well, basically I sat in my brother's lap, watching him play it sometime 97-99. But later I picked it up too, played a lot of Fallout 1, not so much Fallout 2 though. I haven't finished Fallout 2 yet, should do that sometime x) It's not that I don't like it, I just... don't progress.Then I played Fallout 3, liked it as a game, but you noticed more and more things that are like "ehm, ok" or just "wth?!". One thing I didn't like at all was
Optimus Liberty Prime, destroyed the finale, you didn't have to do anything at all. Easiest end-game ever. Then I started playing Fallout Tactics, as I bought the triology pack (had lost the first two games to somewhere) and I liked the graphics somewhat, and the squad-based continuous turn-based combat, but I didn't like that it had very litte RPG elements. You basically just put skillpoints in skills that benefit in combat. And I also died alot and forgetting to save, so I kinda got annoyed and quit it. Didn't get far there either, but try to start again now and then. Then there's Fallout New Vegas. Still hasn't finished it!
So, it's hard, but well
1. Fallout New Vegas, because it's da new [censored]
2. Fallout 1, it's old but it's what started it all and I've played it lots of times.
3. Fallout 2, but haven't finished it.
4. Fallout 3, played it with two characters that were supposed to be different but ended up pretty much the same.
5. Fallout Tactics, but haven't played much.
6. Can't say Fallout:BoS because I've never played it.