Fallout 2 was MUCH bigger than Fallout 1 and had a lot more weapons, side quests etc.
There were some things that I didn't like about Fallout 2. I didn't like the beginning. I ended up having to restart a couple of times because I kept dieing in that stupid temple. The bugs were really annoying. In one quest I kept trying to enter this one area, but the game kept crashing.
(I did eventually get into the area without the game crashing, but it was still really annoying.)
I did enjoy Fallout 3 as well, but there were a lot of things in Fallout 3 that I didn't like.
Half way through the game, you'd have enough caps to buy EVERYTHING! I liked how in Fallout 1 and 2, money was much more difficult to get. Everything was much more expensive in Fallout 1 and 2 than it was in Fallout 3. A Sub Machine gun in Fallout 2 might cost 1000 caps, but a Sub Machine gun in Fallout 3 only costed 300 caps.(or somewhere around)
In the end, I like Fallout 2 more than Fallout 1, but I like Fallout 1 more than Fallout 3.
EDIT: Also, in Fallout 2, you could get a car!