Surely first Fallout was a bit more realistic and it didn't have that many things that are supposed to be fun, but aren't. But that's about the only advantage of the first Fallout. And at the same time it was shorter, the time limit was annoying, and the user interface was slightly worse. This makes Fallout 2 definitely better, although maybe less Fallout-ish than Fallout.
Of all the other games the only one that can compare to it is Arcanum, which was good, very good, but unfortunately not as good as Fallout. Annoying and boring combat and more linear plot unfortunately make it less interesting and decrease its replay value, although it becomes obvious only after you have played through it 3 or more times.
Fallout 2 is long enough to keep playing for a month even if you don't do anything else during that month. It has excellent atmosphere, lots of quests, different ways to develop a character, countless paths through the game, well-balanced turn-based combat, lots of interesting dialogs and much, much more. What else one could possibly want from an RPG?