Although F:NV implemented some cool things that FO:3 didn't contain, companion wheel, ironsights, hardcoe mode, stuff like that, it also got rid of a lot of stuff; stuff that made FO:3 alot more immersive.
- The fact the wastelanders rarely (if ever?) communicate with one another. I am completely shocked as to why they don't in New Vegas, did the writers just forget?
- Although many people will disagree with me, I absoloutely despise the desert setting. Everything is so sparse. One thing I loved about FO:3 was the fact the landscape was so packed. You could walk past an abandoned shack and be 100% sure it was enterable, yet in New Vegas, alot of the buildings are covered in wood. What's the use of that?
- Random Events! Where the hell are the random events? In Fallout 3, you could be traipsing through a forest, only to see a group of slavers firing at a group of escaped slaves. I realise New Vegas does, in some way, contain events. But the only difference is that they are bound to happen, Nipton will always be set on fire by Caesar's Legion, there will always be that same pair of escaped convicts firing at that gang (forgot the name) right before the NCR camp.
- Don't even dare tell me the Fiends are New Vegas' version of Raiders; to hell they are. It seemed the majority of places in F:NV weren't inhabited by enemies, and if they were, it'd be by bloody Cadazores or something similar.
- Although New Vegas did contain the NCR, Caesars Legion etc, you didn't really get this sense of belonging. Perhaps you'll disagree, but you could actually become somewhat of a slaver in Fallout 3, you could become part of the BoS and do their quests, you could become a Regulator and take people's fingers, and vice versa. For me, this is practically non-existant in F:NV.
There's a ton more, but I'm sick of typing. Moral of the story? Fallout New Vegas feels like the predecessor.