Hopefully Fallout 4 will be the overhaul to something a bit more modern. Fallout 3 definitely feels a touch clunky, but maybe that's what I get not starting on it until a year and a half after release... When I briefly played Oblivion, on my old PC which was just a little short on power to make it a smooth experience, I was pretty impressed with the game world and engine. I'm sure when I get to the GOTY that I got for $8.50 off of Steam after I finish Fallout 3 I will feel a bit different.
I'm going to try to wait on picking up New Vegas... not because I don't want to play it or am sick of the engine... just beause spending 50 bucks, then 10 bucks on the DLC as it comes out just doesn't seem cost effective. The $24 I paid for Fallout 3 + all DLC is a great value... I guess I'm just turning into a cheapskate.