On a personal note, I prefer Fallout 3 to New Vegas, but New Vegas is a great addition to the Fallout universe. I received the game for Christmas from a friend a few years ago, but because I had so many things to play, I never got round to playing it through. I recently bought the Ultimate Edition in which all the DLC is available and for 30 dollars was a grand buy. I'm playing it through now, gradually, with Ni no Kuni at the same time, and I'm loving it. Also a surprisingly great voice cast with Rene Auberjonois as Mr. House. I loved it when I discovered he was the voice actor.
I wish I liked this game more, I loved FO3 but this one just didnt do it for me. I didn't get as into the world. 3 felt like a genuine post apocalyptic wasteland whereas this one felt more like a bunch of zany characters in a cartoony version of present day Vegas. I never got that feeling of heading out to explore the vast unknown wasteland alone like I did in the previous game as everywhere I went there was a farmer or a soldier staring at me.
Think the story was better in New Vegas.