Fallout 2 is my fave, the world is huge. (I'm sure it doesn't hurt that my absolute favorite town in all the wastes is "New Reno") Fallout 1 being a close second if I'm just making a simple list, followed by tactics if you count it, then Fallout 3.
I love Fallout 2's world and feeling, additions from the first and improved character creation to make yourself even more unique for every replay even after your 100th
I loved Fallout 1's characters and some of the towns//areas more in some cases (Junk Town, The Hub, The Glow, Necropolis, The Master, Killian.
I loved Fallout 2's many more and improved random encounters//events and I liked the improvements on companions.
(I love you take all button)
Though I have to admit I liked the multiplayed in FOT. RPG wise wasa bit of a let down but as a game was good.
We dont mention that thing that appeared on the console market BOS.
FOT BOS wasn't an rpg is the thing (I liked the game by the way and it still look less creative liberties then Fallout 3 did)