New Vegas is everything Fallout 3 should have been. It pays homage to the originals, being set in a more western environment, has the best RPG elements of any game I've ever played and truly allows you to be whoever you choose. Every single NPC can be killed - or none at all. You can join every faction - or destroy them. Your choices determine the outcome of the wasteland, the characters have depth and reasoning behind their actions and can sway you to change your beliefs. It isn't as linear as "good and evil" choices - the factions you encounter will all be somewhere in the grey.
The DLCs are absolutely amazing (excluding Dead Money, which I personally cannot stand) and add even more depth to the already enticing world. It's a shame Bethesda only care about profit and therefore probably won't allow Obsidian to return to the franchise. New Vegas is a marvel of gaming, the best game of all time and the only true, whole modern fallout experience.