Dr Fallout
Centurion
Fallout 2 easily followed by Fallout 1 then New Vegas, and then Fallout 3.
With Fallout 2, the world is vast, lots of interesting characters and locals, great writing, and I loved the story, not to mention the improved gameplay mechanics. The worst thing about the game are the crashes and bugs. I've had to restart the game numerous times -- too many to count, but I still persevered because the game is that damn good. New Vegas kind of felt the same way, really hard to put down, even with the bugs.
I hated the amount of random encounters. Way too many, I spent literally fighting through 6 tough and repetitive encounters on a normally 20 second trip.