Gaming

I already answered differently, but I want to put out that the STALKER fandom is held together by mods. There are everything from almost invisible bug mods to an entire standalone mod. STALKER is one of those franchises where modding just seems like such a natural fit to round out the world and it’s amazing how the vast majority of mods intend to support the tone of the game rather than just adding in the whims of the mod maker.

Definitely Minecraft, you can turn it into a completely different game

Definitely RimWorld. There's so many mods that improve the base game. From QoL mods that make you wonder why that isn't default in the vanilla game, to mods that complety overhaul the actual win condition. Just overall a really fun, replayability, frustrating game.

Use mods though. It'll make it better. Check out p-music mod while you're at it.

I'd say it is definitly not any TES game. While the engine and released tools give amazing modding capabilities, it is still fine without mods. Back in the day, I spend 800 euro on a videocard just to graphically mod Skyrim. And I have no regrets. But I just as well regularily play on the Switch curreny, as I van continue on the train. Similarily I still booted Oblivion on my PS3 a while back. I feel TES games improve with mods, but aren't tge worst without.

Now for a game that "nééds mods" rather "thas great modding capabilities" I would say the first that comes to mind for me is Mugen. That old fighting game game with 1 stage and 1 character out of the box, but thousands of community made characters, stages, and new character select screens. It caused some videos of the ridiculous (in the best way) fights in a time YT was mainly weird but fun.

Fallout New Vegas for sure, although many of the issues were fixed by the devs over the lifespan of the game. Mods are pretty much vital to run that game properly, however. Many issues with the engine and many core bugs have been fixed by the community, and it's honestly something where once you play with them fixed, it's hard to go back

RimWorld. It's amazing what people can do from QOL to whole new factions or weapons. Amazing and the dev is very helpful during updates to try and not break mod support. Just blown away.

I love vanilla Terraria and Factorio but there are really fun mods out there that expand those games and don't let me play anything else!

I would say the binding of Isaac. The game is amazing but I now really struggle to pay without some quality of life mods

Seconding Rimworld, but even without mods it is an amazing game with easily 1k+ hours of gametime. My favorite mods are QoL mods, or ones that add additional flavor to my colonists. If I could only pick a single mod to install, ever, it would be Common Sense.

Outside of Bethesda and Minecraft, the other one that comes to mind is The Sims. More of a niche following, but for those that love deleting pool ladders, mods are necessary for happiness, flavor, and adding actual challenge.

Civ 4 had a great modded scene. The Colonization remake/spinoff in particular has a must-have mod in the way of The Authentic Colonization. The main game, though, had loads and loads of incredible mods. My personal favorite was the Ryse series of mods, which tried to more accurately model the rise and fall of civilizations via various mechanics. I have a lot of hours in the random map variant of it, Ryse Rand.

A few off the top of my head: StarSector, ARMA, Monster Hunter (both World and Rise) and L4D(2). All of them are solid game already but modding adds so much value to an already good game.

Tabletop Simulator and Garry's mod is all modding, they would be very boring without it. (Tabletop might have the DLC addon content worth playing).

Cities Skylines fixes many of the broken aspects of vanilla and adds things to the point that Paradox added some of them into an enhanced console edition.

Slay the Spire, it's already an amazing game to begin with, but mods allow it to be absolutely insane with customization and cards. Even multiplayer is supported (Together in Spire) and works quite well!

American/Euro Truck Sim has a multitude of mods that add great stuff and even more realism to the game.

Call of Duty Black Ops 3 is more or less a bog-standard shooting game without mods, but the number of crazy, funny and innovative maps for zombies gives it an insane amount of replayability.

Late to this post but to me it's Minecraft. It has such an insane amount of replayability and can be turned into a totally different game depending on the mods and whatnot.

Rimworld. The Vanilla Expanded mods alone have more content than the base game + all the DLCs

minecraft for sure

Another vote for RimWorld, though I want to point out that the game is perfectly playable without mods, too. It is not uncommon to see someone with hundreds of mods, but the vanilla game is just as fun. People have logged thousands of hours without mods.

There are plenty of older games where running some kind of widescreen or compatibility mod to get it working on newer hardware is the only way to get it running well, but that's kind of a boring techie answer.

In the spirit of the question, I'd say Fallout 4. The base game has a story I don't care about, factions that make no sense, and very little in the feeling of actual threat. I usually run between 200 and 300 mods to turn it into a truly post apocalyptic hellscape with functional radiation storms, low visibility in dust storms, darker night, less HUD clutter, more ghouls, proper flashlights, retuned weapon damage so things aren't so spongy, lots of new gear and weapons (I add in real guns but try to be tasteful and not add too much super modern tacticool stuff, but more cold war and vintage guns), backpacks, re-dress the Minutemen so they don't look like 1776 LARPers. Add tons of new sidequests and stories to find. The world becomes, this amazing, terrifying place to just explore and forget about the main plot. Returning home to my concrete walled safe settlement and my personal bunker living space really feels earned after exploring.

I played vanilla Stardew Valley once, and now I'm on my second go around, and I've installed a bunch of qol mods so that I don't have to keep checking the wiki and my collections to see if I should keep or sell this item I got because I don't know if I need it for an achievement, and now I have a notification that it's an NPC's birthday and I can just check to see if I own or am carrying an item they have. It just makes the game less stressful for a completionist like me.

not modding much, but what people do with skyrim is amazing

Mass Effect: Andromeda

Half-Life 1

Skyrim