Great game, lives up to Fallout 3 but doesn't really outdo it. Fallout 3 definitely had the upper hand on every aspect.
Gameplay : The gameplay remains unchanged from Fallout 3. With the addition of new weapons/items, a new Survival mode which throws in sleep/hunger/hydration needs, weapon sights, and enemies, the game remains almost like DLC for Fallout 3. The weapons are ever more sweet, the items list has been improved, and the enemies are challenging keeping the game fresh so anyone whos played Fallout 3 can hop right in and play as if it were nothing yet it remains challenging. The only issue is that the game tends to freeze up alot (since its quite huge) which is a pain but autosaves help reduce the risk of losing your data. Apart from the new additions, this is once again Fallout 3 set in a different location with a few upgrades.
The World Map: My biggest complaint with New Vegas. This world is so boring and bland compared to the Capital Wasteland of Fallout 3. The Mojave is a waste, desert wasteland with little towns scattered about and only one small city (Vegas). Apart from that, its just miles of nothing, cliffs, and enemies with fillers thrown in. Compared to Fallout 3, this is just a let down entirely. The locales and culture are also less interesting than Fallout 3, focusing on a Old West theme (wtf?) of cowboys and spaghetti westerns. Considering all the potential this game had, this is the reason for my reduced score. It was just a serious letdown going from the massive, Urban Capital wasteland to a barren, cowboy-inspired desert wasteland with nothing worth exploring unless you're on a quest there. If you can get by this large downgrade, this game is great and a good follow up to Fallout 3. It stays loyal to the fun, but I feel the developers could've made the setting much more interesting and innovative than this.