But so that this isn't spam:
I don't understand how New Vegas could be more like Oblivion. Dungeons? No, I don't want copy-pasted dungeons all over the place. Side quests? No, I don't want Oblivion's many but very short side quests. Story? I dunno, I didn't really like how Oblivion's story was so urgent, and forced you to jump right unless you want the game to feel very strange("Hey, you gotta find the emperor's son and save Tamriel from the Oblivion crisis!" Nope, I think I'll spend a hundred hours killing mudcrabs). Cities? Not really. Imperial City is a huge disappointment, considering it is supposed to be huge. The city of Vegas seems good so far though.
I just don't see how New Vegas can benefit from being like Oblivion in any major way.
I loved Oblivion, and recently spent a few weeks of vacation in Cyrodiil before starting my mod conversion to FNV, and I was surprised at just how different some aspects of Oblivion are compared to Fallout 3 (considering the latter uses an upgraded engine of the former). Some things I really Liked about Oblivion that wasn't as strong or present in Fallout 3:
1. There were many Big cities, or big by standards of the times, and this was a definite contrast between the games. More cities meant more to do/explore, and the scale seems so much bigger in Cyrodiil than in the DC Wasteland.
2. 71038741283740182347 quests - OM MY. I actually suspect that FNV will be more like Oblivion than Fallout3 in the number of quests and dialogue, but I think FNV will go leaps beyond Oblivion in the variety of the voice acting present.
3. Oblivion had many, Many secondary locations - not everything a dungeon and some places similar to others. I loved this, it made the world seem so massive and that it would take weeks and weeks to do it all even though I knew most of it like my own backyard. Fallout3 just doesn't approach this level of scale.
4. Battle/encounters take longer in Oblivion than in Fallout3, especially if I'm a sniper or have a bag of 100 grenades and a few nukes. Even with Midas Magic I don't have that kind of killing power in Oblivion, things take a bit longer and thus required a bit more strategy from me. I like this contrast, but I think FNV will be very much like Fallout3 in death-rate/speed of moving over terrain versus Oblivion.
5. Oblivion Alchemy / Reagent collection - Mmmmmmmmm. Loved this feature, nothing like it in Fo3. I'm hoping the FNV weapon/ammo in-game modding and cooking will bring some of this flavor back to the scene.
6. Slower leveling, more balanced skills/powers, much harder to become a God in Oblivion than in Fallout3. I'm hoping FNV is more balanced and challenging like Oblivion was in this regard.
7. For me Oblivion would generate months of play-time the first time through each character, whereas Fallout3 was 2 weeks by comparison per play-through. Hoping for more Oblivion-longevity in FNV!
These are just my views, not the gospel on the differences between Oblivion and Fallout3 - both were fabulous games and hooked me good, FNV can't do wrong to be like either of them in success if nothing else.

Miax