The thing about turn-based is that it's all about levelling your character, much like tabletop RPG. You design a great character and they'll do well in the situations you've designed them for. In an fps (or equivalent), you can design a shitty character, and just be quick with your RT finger. I actually like the mix that Fallout 3 has. I love the levelling side, and sometimes that's fine on its own, but the balance they struck in FO3 was pretty much spot on for me.
So far as the original Fallouts go, I tried to play the first one back when FO3 came out and I couldn't afford it. Now I play some old-school games, and some point-and-click games, but I found Fallout 1 irretrievably ugly, and the story didn't really draw me in in the opening hour or so. So I stopped playing it. I know that there are people who love them. I also know (though I don't understand) that there are some people who prefer them over the most modern incarnation. For me, there's not much they could fix about Fallout 3 to make a better post-apocalyptic role-playing game.