I personally think Fallout 2 was the best as it was short and sweet, it didn't have a time limit thus more leisurely, and it had humor but that is a negative for some people.
Top 3 has to be new Vegas, 4 and 3 in that order but what let's me down for new Vegas is the battle for hoover dam, I get it is a big part of whats going on between every faction but its just meh
I agree with fallout 3. All fallout games have their strengths and weaknesses, but 3 seems to have a good balance between story and gameplay. Fallout 3 was also my fist Bethesda title so I’m kinda biased towards it due to it introducing to one of my favorite publishers