New Vegas' quality of life improvements made it better than 3 to me.
I LOVED Fallout: New Vegas. So far it's the only one that I've gone back and played several times. The only thing that sucked about it for me what the sheer amount of bugs in the game, thankfully most of them where patched.
This just makes me want to go back and start up that evil melee chr I've wanted to play for a while.
Most everyone i know got into fallout with Fallout 3. Therefore I would say oblivion is the best fallout game. Oblivion > Fallout 3 in so many ways.
I put a good 200+ hours into Fallout 3. One of my top games.
I played New Vegas when it came out but, it just didn't seem fun compared to 3. I kinda had to force myself to get through it. I'm eventually going to get the extra content for it when it goes on sale, so I hope that's better.
I've only played Fallout 3 and New Vegas, and I loved them both, but I think I preferred New Vegas.