It's highly heretical but I always found Tactics and New Vegas the only games in the Fallout series that I enjoy.
While the storyline and characters in the first two Fallout games were really good, the god awful and slow combat turned me completely off it. Coupled that with a terrible clunky UI and rather dated graphics. It's rather hard for a person who didn't grow up with the games to get invested.
While I want to play Fallout for the characters and world I found the gameplay just too grating and getting in the way too much. That said I could just be because I tend to prefer realtime/pseudo-realtime-pausable combat over turn based.
Tactics on the other hand has the best combat in the pre-FPS generation which makes up for pretty much all the short comings in the storyline. Sure the world feels a lot less like Fallout and more like Mad Max but it seemed to worked for the gameplay.
I did find that low level play seemed to be a little bit more tactical than higher level when you get all the crazy weapons/perks and have to mow down deathclaws and robots, I much prefered the early rifle crawls, shotgun storming and sneaking grenade throws.
Also while I was never a fan of the Brotherhood of Steel it was nice to see them being painted in a much worse light than the previous stories. Those xenophobic technology hoarders can go and plasma themselves as far as I'm concerned.
Fallout 3 was the typical Bethesda mess and isn't worth discussing.
Fallout New Vegas had a nice expanded world and although the combat was improved over FO3 it didn't hurt to install a couple combat rebalance mods. I still rate it as the best Fallout game even if the combat doesn't resemble the originals. World was fleshed out, some decent themes were explored and the storyline was nicely constructed with nothing too crazy going on. Obsidian is a highly underrated studio who just need a single publisher to not rush one of their games so they can finally get over the finishing mark and make a masterpiece, FO:NV and KOTOR II were sooo close.