fallout 3 was better than new vegas.
it ran better, had less crippling bugs,
Fallout New Vegas is easier to get running on modern systems and it doesn't run on GFWL. Also the Steam version of Fallout 3 is automatically better than the disk based GFWL versions because it removed key checking for GFWL. So it's easier to remove.
guns felt better (I SAID IT),
In Fallout 3 the guns were more like a typical FPS in that there were only a few of them. However as a result unlike most rpgs you typically just stuck to one.
Like whenever I played a gun based character in Fallout 3 I mostly just used the hunting rifle, assault rifle and combat shotgun, and would just use those throughout the game, repairing them as I went. By comparison in New Vegas the first long range rifle you get (the Varmit rifle) is outclassed really early on once you get to Primm and find the Cowboy repeater. And that gets outclassed as well, and so on and so forth. The game is more like an RPG in that regard and it helps all the guns in the game were upgradeable. It also had additional forms of ammunition to compensate for the Damage Threshold (Which only made the enemies in the game less bullet spongey because you could immediately counter how much health they had with a more expensive armor piercing round).
However I still freely admit that the guns in both F3 and NV were pretty badly implemented, and whenever I replay the game now I typically go as a melee or energy based character.
and the companions were more interesting.
The companions in Fallout 3 have at most a couple lines of backstory. The most in depth backstory for any of them is probably Fawkes.
By comparison in New Vegas, every companion has a side quest, some have several. In the case of Arcade Ganon he has a questline that spans the whole game and provides backstory on the Enclave, and is also the only way to get power armor training without the Brotherhood of Steel.
Also in New Vegas morality wasn't a concern, your companions cared more for who you sided with during the story. Like Boone would leave instantly if you killed too many NCR troopers. This was not the case in Fallout 3 where companions just cared about whether you did good or bad things.
the story may not have been as solid but at least it felt contained and directed, whereas nv was simply all over the place.
Fallout 3's storyline was linear and much shorter. New Vegas's was much more open ended and encouraged exploration.
Specifically the game tells you right at the start that Benny is most likely at the Strip, and you can see New Vegas from Goodsprings. But the North West passage to New Vegas is full of Cazadores and deathclaws. It's still very possible to just outrun them and go to the Strip, bypassing most of the first half of the game. This is exactly how Fallout 1 and Fallout 2 were designed. In Fallout 1 it's possible to complete the whole game by just going to the Mariposa Military base, destroying the Vats and then killing the Master.
After you confront Benny then the game becomes significantly open ended and allows for several distinctively different runthroughs of the game. Like playing as an NCR requires you to do vastly different quests than playing as a Legionnaire (a good example is how when you play as an NCR/Wildcard/House you have to protect the president from being assassinated. Whereas when you play as a Legionnaire you have to assassinate him and you have like 6 different ways to do it).
This has already been said but:
Personally, I think Fallout: new vegas is boring as fuck. I walked around and saw dick bupkis other than baby geckos charging at me like retards. Fallout 3, on the other hand, had plenty to see right from the get go.
There's a town featuring an elaborately designed roller coaster, a prison, a shack surrounded by ghouls and radioactive water, and a great deal of other locations just south of Goodsprings. Going even farther there's Camp Searchlight which is one of the best locations in the entire series thus far. (and is ridiculously hard til much later in the game)
That's not counting the mass amount of extremely well designed locations in New Vegas later on in the game. Such as the extremely good writing in the different Vaults (Vault 11 and 22 especially), Caesar's camp which has one of the best ingame conversations in the entire game, the sewer segments under Westside (which are probably my favorite sewers in any game ever surprisingly), the Great Khan encampment, Black Mountain, Jacobstown, etc. There's a great deal of really unique locations in New Vegas in total and I remember all of the individual settlements much more than I did in F3.
Fallout 3 had a great sense of atmosphere, and really felt like the shattered remnants of america, New vegas seemed like such an odd place for fallout because it was just so... developed... and not destroyed.
Fallout 3 and New Vegas take place 200 years after the bombs fell. Fallout 3 has a pretty erroneous plot in that it revolves around irradiated water, when in reality radiation doesn't stay in water for that long. Fallout 3 also was very disconnected to the rest of it's series since the NCR was fully established in Fallout 2. (And in Fallout 2 they have completely rebuilt cities with paved roads, their own currency and electricity).
New Vegas fans always brag about more guns and creatures and shit, but what's the point if there's nothing fun to do with them? New Vegas just looks so empty and barren, I could walk around a real desert shooting at insects with a slingshot and get the same amount of excitement.
I've already mentioned some of the other locations in the game outside of Goodsprings. It's also not counting the DLC either. Which each feature an overarching story over the course of the entire game that can be played in any order and they each elaborate on some bit of lore that was left ambiguous and vague in the vanilla game.