I do not recall ever replaying any of them. I'm sure that was partly due to my temperment at the time, but I think another big reason is just that I didn't enjoy them as much as I do FO3 and NV.
I tried to play FO1 on Steam right before FO3 came out. I left the vault, died on my way out of the cave filled with rats, reloaded, made it out, made my way to a city, (Necropolis I think) got in trouble by touching something that apparently the ghouls didn't want me to touch, got killed (probably the 9th time for the game that took about 45 mintues) and I quit. I couldn't take it anymore. The game was designed to run on a 486 or less right? Why was everything taking forever? I'd click a spot to go to, and the little animation would take forever to get there. I was running a dual core, 3 ghz machine with more ram than I'd ever dreamed of back when FO1 came out and a videocard that had not yet been conceived or dreamt of. Why was it as slow as it was back then?
I couldn't "get into" my character because I had no understanding of why my actions were having such negative consequences. Everything was slow, which is fine for Chess, but not for a one player game where I am not building an empire. In Civ, I have to make decisions, tons of them, across a turn. I get why that should be slow. This shouldn't be.
Another note. I have nothing against isometric gaming, though I think it would be hard to implement for the console and make fun. That said, I can't handle turn based RPG's anymore. Baldur's Gate et al, got it right when they made the action "pauseable" but combat was otherwise real-time.
The first time I played a RTS, I couldn't play for the life of me. I still can't. I don't like it. That said, turn-based RPG's, same thing now. I can't play it. I never enjoyed the final fantasy games, and one big reason was the turn based combat. As I said, I loved FO1 and 2. FO2 was hysterical, though it seemed to take away from it's believability. FO1 will remain a fond memory, but I can't go wandering past memory lane and into, "try it again road" because the gameplay just doesn't do anything for me.
Maybe I've been spoon fed for too long. But I like that games will tell me when someone's going to be pissed when I grab something. Maybe I'm lazy, but for me, having to reload often takes me out of the game, even if a load is fast.
I have not properly played FO1 or 2 in over 10 years now. I never did replay them, I'm not entirely sure why, though I played FO3 3 times, and will probably play FONV 4 or more times (on 2nd play-through now). I wonder if it was the fact that they were so slow.
I guess I just wonder, am I the only fan of the originals that can't play them now? Who prefers FO3 and NV?
On that note, I am definitely in the group that prefers NV over 3.