ok this is weird i want to know why my computer can run fallout 3 on ultra graphics but when it come to fallout new vegas my computer struggles even run it on lowest setting was there even graphic improvements?

No.

Try 'verify games cache' on the FNV properties tab in your Steam menu (run Steam.exe or your Steam shortcut). It helps the game run better if the cache is okay (cut my freezes, crashes and lags by about half - I had two files corrupted). This is for PC, not sure what arrangement consoles have though.

Edit:

Another work around is to go into your graphic card's menu, and try different settings. I dropped HDR from the graphics, and that cut a lot of the stutter and lag out.

This is one of arguments consols can finally use against PC users in flame wars....

http://www.youtube.com/watch?v=XRGd0gD0QNE

Sticks and stones can break our bones, but we can totally outmod them....