I think that Bethesda did a perfect job on Fallout 3. They have shown what an ideal Fallout would look like. And after 200 years of Fallout, there would end up being +1 rad per second. And in highly radiated areas, there would end up being +2-+10 rads per second. Nothing wrong with that. As for the color...sure, it's not the gleaming Las Vegas-type setting, but it's not supposed to be. It's supposed to display a true post-apocalyptic lonesome setting...which it did. Plus, without that type of feel(Which hardly no other RPG game has displayed before)...Fallout 3 wouldn't be as special as it is. New Vegas brought most of the weapons, we see in games today and created a world where Highrolling and the strip were desired. I've seen a lot of games do this before.
I guess, many are not fond of Fallout 3, just because of its differences from other games. Fallout 3 is a survival game...where as New Vegas comes off more as a War/Campaign game. People who are used to these Campaign games, such as Call Of Duty, Battlefield, Killzone, Renaissance, BioShock, DeadSpace, Minecraft, etc, have more relation to a game like Fallout New Vegas, than Fallout 3. A game like Fallout 3 doesn't come around often.
I think you got that last comparison wrong, people who like Call of Duty tend to hate Fallout and if they would choose between the two they would probably pick Fallout 3 it giving the illusion of a non-linear experience, being entirely focused on exploration and whatever Todd 'MichaelBayawesome-sauce' Howard decides to throw at them like giant robots, black stormtrooper people, dumb hulks with big weapons and more lore inconsistencies then you could shake two sticks at.
New Vegas attracts fans of the original Fallout's(the ones before Fallout "3") because it has interesting dialogue, complex characters, a wasteland that is explained and makes sense for the time it is set in and what happened to it, the reintroducing of many principles from the previous Fallout's that Bethesda decided were too restrictive or complex(Damage Threshold, no playing after the ending, different ammo types, the lengthened perk ratio, choice, reputation) and in fact it was made by Obsidian who has many of Fallout's original creators.
I apologize for this rant. I usually try not to project my true feelings about Fallout 3(which is still a good, if flawed, game) in the Fallout 3 section, but I feel like some things need to be said.