If you liked Fallout 3 than you will love New Vegas
Story: ( Spoilers Sort of ?) You have to give a package to a guy and he shoots you in the face after that some doctor fixes you and your on your way thats the start of the game but to find out the ending its really up to you how you want it to end and ends by the the choices you make and not some set path a NPC.
Gameplay: If you like fallout 3s game play than you will love new vegas it has better third person and when in first person you can aim down your sights which is a huge improvement over Fallout 3s which was just zooming your weapon a bit. Plus the are more new enemies for you to blast away and some old ones too and lets not for get that the vats which hasnt changed much but is fine by me since its still fun to blast em away in slow mo.
Graphics: Not that differnat from fallout 3s but there are slight improvements.
Sound and Music: The sound is great in new vegas its has new and much better voice actors and cool weapon sounds. Plus the music is just great and is full of 50s and 60s type music that fits very well with the whole feel of the game.
Overall: Now I know somepeople are having problems with this game and thats me included but after you look past the glitchs and errors this game has every now and than its a really good game that must be played if you liked Fallout 3 or even Just RPGs so trust me this game is really fun and I had a blast with it and hopefully you will too.