Please name great games with infinite replay factor

I'd say XCOM 2 with War of the Chosen DLC on if you are into turn based strategy games.

Just Cause franchise

try out killing floor 2

Mount & Blade: Warband - skyrim - fallout new vegas - Final Fantasy X/X-2 HD Remaster

Tales of Maj'Eyal, a roguelike with a huge number of classes, each allowing different builds. And that's not taking in account custom classes or mods.

Terraria, most people see it as a 2D Minecraft but in truth it's more of a Metroid + Diablo combo where you can modify the map.

The Sims, although it's pretty much one of these games where you have to set your own goals.

Any 4x game (Civilization, Endless Legend etc) since there are many randomizable factors.

Well, since it doesn't look like it has been mentioned yet my vote will go towards Deep Rock Galactic which while yes it is Early Access is still very polished. People say combination of Minecraft and Left 4 Dead and I would have to agree. Every new mission you choose is a completely new procedural-generated cave system. You can play alone or online, play/level up different classes with different abilities and upgrades and change mission length/complexity/enemy difficulty. It is also fun to play, which is probably most important.

Rainbow Six Siege, im at 1400 hours and still not tired of it. It can be hard to get into though :)

Black and White
Black and white 2
recettear
just about any rng \ rogue like.
bunker punks
e.y.e divine cybermancy
kingdom new lands
legend of grimrock
legend of grimrock 2
satelite reign? - although it had an abysmal ending
undertale
wasted
RISK OF RAIN!!!
i guess 100% 200% orange juice series since theyre mario party board like games. although i only played 100% for like 1 hour.
airmech strike since its a cutesy multiplayer moba type
alien swarm reactive drop because multiplayer
planetside 2 cuz multiplayer
maybe its just me n nostalgia since i grew up beating this game a few times, even though its only '2 different endings' Bet on Soldier
contagion
... i could go down my entire library
minecraft :D

Fallout: New Vegas, there is easily enough for hundreds of hours without adding any major mods into the mix. With mods? You could play for thousands of hours and have a different experience each time you start a new game.

Ignore the measly 659 hours it shows, I easily have over 2,000 hours. I had no internet access for about a year and this is what I spent most of my free time on, I would download mods onto a USB stick at the local library.

Thief (2 the metal age) basically due to over 15 years of fanmissions and still occasionall updates.

Some games:
Disgaea series, lots of grinding in item world and rising stats
ClaDun series for grinding
Civilization series, strategy
Skyrim arpg with some mods to keep it fresh (Fallouts etc would work also)
Pinball Arcade, Zaccaria Pinball, Pinball Fx3 if you like pinball
American Truck Simulator/Euro Truck Simulator 2 if you are curious about driving trucks
Beat Hazard series, arcade shooter on your own music
Touhou series :P, Get good Lunatic 1 life full run :P
Mortal Kombat, Skullgirls, etc online fighting games, get good :P
Minecraft block building, etc, enough said
Starbound kinda 2d minecraft but not really

I´ve seen Steam profiles with +3K hours on Red Orchestra Ostfront 41-45.
Zombie Army Trilogy could easily gives you +50 hours. I played with a guy with +500.
Both are online multiplayer.

Don't know if someone mentioned Stardew Valley. Easy 100 hs, and maybe much much more.

Also:

• Sunless Sea. Deep storytelling with new quest being added periodically.

I've put quite a few hours into crafting / survival games. I think they're best played with friends, but you can solo them too. Probably an obvious pick, but I've put hundreds of hours into minecraft and it's various mods. I started with Tekkit and moved to Feed The Beast, current favorite is the Age of Engineering FTB pack which you can sink tons of time into. I've also had a lot of fun with ARK: Survival Evolved, though it does require a pretty beefy rig to run well, and is more difficult to solo (though you could host your own server and modify the crafting/taming/harvesting times to make it less grindy).

Spelunky

and old game called shadow of memory
it had like 7 endings depending on what choices you make during gameplay and each ending is unique and deferent
there is also borderlands 2

great games with plot
Arcanum: Of Steamworks and Magic Obscura
Neverwinter Nights 1-2
Pathfinder:Kingmaker
Pillars of Eternity 1-2
Tyranny
Underrail
Age of Decadance

Book of Demons (if you have nostalgie about Diablo)

yea, there are also too many rogue-like games with no plot and randomly generated levels:
https://store.steampowered.com/tags/en/Rogue-like/#p=0&tab=ConcurrentUsers
27 pages of good games (almost) (even claustraphobia:downward struggle and rogue's tale)

https://store.steampowered.com/app/4500/STALKER_Shadow_of_Chernobyl/ + mods from https://www.moddb.com/

https://store.steampowered.com/app/262060/Darkest_Dungeon/

https://store.steampowered.com/app/238960/Path_of_Exile/

https://store.steampowered.com/bundle/8133/Borderlands_The_Handsome_Collection/

And, as for me - it's GOTY (also, ton of ways to replay included) https://store.steampowered.com/app/863550/HITMAN_2/

Arcanum
Death Skid Marks
Nuclear Throne
Enter the Gungeon
Streets of Rage Remake with downloadable levels

4X games are amazing for replayability.

Actually it depends for everyone.
For example I would be bored after 1 hour in Skyrim, but some fanatics say they have hundreds or thousand of hours.

For me it's Dark Souls.
Tomb Raider series. I mean real Tomb Raider, not reboot.
Half-Life, at least 2. But I think first too.
Actually I replay many of games I like. So it's hard to tell. If I like the game, I want to play it again. Otherwise I wouldn't like it?

Depends what type of games you like but ok.

Some stuff I have:
Mount and Blade Warband (Especially with mods)
Most Paradox games (Crusader Kings, Europa Universalis etc.)
Terraria
Starbound
Civilisation series
Endless Space/ Endless Legend
Minecraft (Yeah, I know, but when you ask for infinite replay value what else do you expect)
Osu! (Really sucks you in if it's your type of game)

For a more detailed answer, I suppose anything that has procedurally generated content is a good way to start. Most roguelites, roguelikes and etc. would fit this. Then you have sandbox games like terraria, starbound minecraft etc. which are also procedurally generated. Both of these focus on infinite replayability.
Then you have most grand strategy games and some strategy games. Stuff from paradox is a good way to go because even one playthrough of say, EUIV, can take tens or hundreds of hours, and even if you just did 1 playthrough per country that's tons already. Hunting for achievements adds so much more too. This applies to most games of the type, though maybe not as high in the timescale. 4X strategy games also heavily rely on replayability, such as civilisation or endless legend.
Then you have arcade-type games, likes Osu!, which if you like them, there is no real limit to how much you can play. Hell, I have over a hundred hours spent just on one pinball game.

There's also dungeon crawler RPGs, like Diablo or Path of Exile, though I haven't really played them too much. The scripted campaign is what it is, but it's when you reach the end that you have the replayability of the procedurally generated dungeons
Lastly, there are the open-world RPG games. The reason I didn't list any earlier because they don't really have infinite playtime, but they have a potential for a huge playtime. Skyrim is one of the more popular games, allowing hundreds and thousands of hours easily, due to the many characters, a huge amount of quests and roleplay capabilities.

For multiplayer games, I would say fps games like CSGO, Rainbow 6 Siege, etc. offer infinite playtime, if you really like shooting others :P

Strategy-games:
Civ, Paradox-titles(Crusader, Europa, Stellaris), maybe Total War(Warhammer has pretty different factions),
Sports:
Football Manager or race-sims like Dirt Rally
Survival:
Don't Starve, Rimworld
Simulators:
Guild(can't add it as certain genre), Sims!, X3(or dive deeper, Freelancer, Elite), Kerbal Space Program
RPG:
Mount and Blade is the most various for content, I think.
Roguelike:
Many of them, If not Dwarf Fortress then some ADOM, for example