Well, take this for what it’s worth since I’m personally of the 1 > NV > 2 > 3 > 4 > Tactics/76 > BoS persuasion, so our preferences probably overlap and I might not be the best person to speak to why some prefer 3. But here’s my best take at why some people might genuinely prefer Fallout 3 over New Vegas.

1. The world is more exploration-friendly.

Fallout 3 drops you near the center of the map, uses fewer invisible walls, and basically lets you run in any direction from the moment you leave the vault. Some of those design choices come at the cost of immersion and a clear sense of progression, but for players who just want to wander and explore, 3 scratches that itch.

New Vegas, by contrast, funnels players through a “racetrack” loop that eventually leads you to the Strip, then sends you outward to deal with the major factions. This structure reinforces the narrative pacing and supports the game’s strong story design, but it does reduce the sense of open-ended freedom.

2. Fallout 3’s dungeons are more extensive.

Most of 3’s dungeons are longer, more combat-heavy, and offer more substantial looting/scavenging opportunities, including bobbleheads and unique gear. While New Vegas has brilliantly written locations (Looking at you Vault 11), many of its buildings amount to one or two rooms, largely due to the game’s famously short development cycle.

For players who enjoy the simple rhythm of clearing out big spaces and gathering loot, Fallout 3 offers more of that classic “delve and scavenge” gameplay, even if its combat system is fairly "mid".

3. The atmosphere feels more traditionally “post-apocalyptic.”

This one is entirely subjective, but many players feel that Fallout 3’s bleak, bombed-out wasteland better captures the classic “nuclear apocalypse” aesthetic. New Vegas has richer world-building, themes more aligned with Fallout 1 and 2, and a more realistic sense of a society rebuilding after centuries, but its tone is often more eccentric than apocalyptic. For some players, that makes 3 easier to get immersed in.

For the record, I still personally believe New Vegas is the stronger game. (Outside of "atmospheric reasons") Most of the things Fallout 3 excels at are also done just as well (or better) in Oblivion and Skyrim. But what New Vegas does well, player agency and narrative depth, is something very few non-Isometric CRPG games even attempt, and even fewer do it even half as good. So comparing the two within their respective genre "spiritual siblings", NV is a exemplary title within its peers, while 3 is kinda just "one of the post Morrowind Bethesda" games (where Skyrim seems to reign as the champion).

Still, Fallout 3 delivers the “meditative, exploration-driven gameplay” that Bethesda built its reputation on from Oblivion onwards. For players who fell in love with that formula (especially those who entered the series with 3), New Vegas can feel like a departure from what they enjoy about the series.

And honestly, that’s one of my favorite things about Fallout: every game is a departure from the last. Fallout 2 shifted the tone dramatically from Fallout 1. Fallout 3 reinvented the franchise entirely. New Vegas reworked 3’s skeleton into something more narrative-focused. Fallout 4 emphasized crafting and building. Fallout 76 went multiplayer. No matter which game is your favorite, each one brings something unique to the table.

Anyway, I could talk about this stuff until the actual apocalypse, but I'll end it here. But hopefully this helps explain why some people genuinely prefer Fallout 3 over New Vegas.

I think it's just new Vegas stans are very vocal lmao

As someone else who prefers 3, I think that it's more fun to explore and generally has a better atmosphere. New Vegas has better writing but the world feels empty. 3 more fun to actually play. Honestly, I'd probably take 4 over NV for the same reason.

1/2 I haven't managed to get into. At all.

ETA - I was also never really interested in the wild west as a setting, so NV has a bit of an uphill battle from the start.

I don't think it's better than NV as a whole, but there are things it does do better. Probably the biggest is the random events. They have a lot more variety and interaction then NV. You might end up with a BoS Remnant group spawn and a Deathclaw, and they'll just start fighting. NV doesn't really have this. It's much more contained and scripted.

In this way, 3 is closer to 1 and 2 than NV is. A large part of the first two games are the random events as you travel the world. NV is almost entirely predictable, with the same things always being at the same spots. 1,2, and 3 are fairly unpredictable while exploring. Landmarks will be the same, but what you see along the way usually won't be.

I've seen a ton of debate over 3 and New Vegas. People have said New Vegas is too small or too empty. I don't get that at all, but I've definitely seen several people saying so in different venues.

Not quiet at all. Lots of people loved 3. I’m old enough to remember when NV was the red headed stepchild of the series. I don’t think you’ve picked up on the fact that New Vegas is a cult hit. It didn’t become “everyone’s favorite “ for close to a decade at least after its release.

“What does FO3 have over New Vegas”? Well at the time New Vegas was regarded as a cheap knockoff of FO3. It didn’t do much to innovate from FO3 and played like more of a Fallout 3.5 which people resented. It also had a less bleak and more “Zany” tone to it than FO3 did which people weren’t a big fan of. Also by that point Bethesda had a bad reputation for releasing buggy games and NV somehow managed to be buggier and more broken than any Bethesda game had been, and what’s worse is it was never even to this day fixed as several major components of the game remain completely broken without fan patches.

I mean, I love NV and think it's by far the best 3D Fallout, but it's also got a ton of performance and bug issues. Partly due to the engine they were working with and the insane development cycle, but still. The game isn't without issues. It's famously unstable and buggy if played without mods. I also think it needs mentioning that a lot of the assets look out of place, because they are. The game had such a short development cycle that a lot of them are just reused FO3 assets.

I love it, but there is a reason so many people recommend something like the Viva New Vegas modlist even for a first playthrough.