Fallout 1 has a couple of limitations in bad dialogue writing, Fallout 2 was perfect (bugs included).
Fallout 3 was disappointing, not funny enough, and I didn't sympathise with anyone I met - if 640 x 480 isometric has me feeling more about characters than bump-mapped, bloom lit blah blah pretty people, then there's something wrong, methinks.
Fallout Tactics was pretty good, but I never played it for long enough to develop a really good idea about it. Was there a major overarching plotline, or was it just squad based strategy, as I suspect?