I tried Fallout 1,2 and Tactics, but I disliked all three.
That style of rpg doesn't fit well with me.
So, out of the two modern Fallout games, my favourite is Fallout 3.
It had a cool storyline and was really rememberable, and the DLC was really good.
Fallout New Vegas was good too, but the boring desert cowboy theme pissed me off after a while, the storyline wasn't as enthralling IMO, and the fact that you couldn't continue afterwards pissed me off to no end.
I know the reasons, in that there are so many choices and outcomes, that you'd need a massive game to follow on with all the different results, but even so, I can't help but feel disappointed. I dislike the idea of my actions in a non-linear game suddenly meaning naff all and having to restart.
Atleast Fallout 3 had the Broken Steel DLC and let me continue.
Also, I didn't like the New Vegas DLC at all. I haven't found any of them to be interesting or as fun as any FO3 DLC, and none of them have stuck with me as something to remember.