Fallout New Vegas was much better in my opinion and I had a lot of fun playing it, I had played Fallout 3 before but never finished it despite many attempts. I felt New Vegas better captured the humour, story/writing and feel of the original games.
Neither are as good as Fallout 2, this was a masterpiece of a game back in its day, I think the biggest disappointment with the games was the horrible buggy engine which felt very float consolized, I had to tinker with FPS locks, multi-threading issues, FOV, advanced graphics detail, and deal with crashing with both FO3 and FONV. Had these issues not existed out of the box the experience would have been a lot better, I'm sure.