Portal and Portal 2!

The older Sam and Max games were great.

HITMAN! The core story/cutscenes form a very serious, grim premise. But, the actual gameplay, and the writing of the many dozens of NPCs in each level, is filled with humorous charm and tongue-in-cheek Bond-eque silliness. Characters will acknowledge 47's often paper-thin disguises, make silly remarks about excuses to take off early, or alluding to how horrible it would be if some freak accident occurred. Plus, the mechanics can involve things like dropping banana peels for people to slip on, or luring people with a cartoony explosive rubber duck.

It takes a bit of time to get used to how the game wants you to explore, and stop trying to brute-force it like a stealth game. Quite often, some of the main intended ways of going about a mission involve little to no stealth. It's a lot of fun and very replayable.

The Monkey Island games come to mind. A Bard's Tale maybe?

Esoteric Ebb

It's Disco Elysium, but you're a cleric in D&D in a nutshell.

South Park: The Stick of Truth and its sequel were really funny and the RPG gameplay was a lot more fun than I expected. I’ll also second the recommendation for the Monkey Island series.

The original ace Attorney trilogy is pretty good with humor, some people enjoy the humor in the somnium files, yazuka zero's side content is pretty funny.

Grim Fandango!

Never has a game made me laugh out loud like when I first discovered it. Clever humour, unique characters, and each line of dialogue is packed with effortless charm and wit. Not to mention the philosophical themes disguised as one man's quirky Day of the Dead -themed quest to get to the afterlife.

The puzzles are a product of its time so a walkthrough might be needed. But that's forgivable for the game's big picture.

Wish I could wipe my memory of it and play it all over again.

People (not me), seemed to really like Thank Goodness You're Here. Undertale is a popular one. Date Everything seemed funny from what I saw of it, and if playing with friends things like peak, baby steps, or getting over it. Lots of different genres there, but steam also has a tag for comedy games. Even if you don't end up buying it on steam, you can always check that out in case you don't get enough options via comments.

There Is No Game. It's not very funny, but still pretty funny.

Unmetal is a fun spoof on Metal Gear/MGS games

If you're enjoying The Stanley Parable, you'll probably like Do Not Press The Button To Destroy The Multiverse.

Have you got the deluxe edition of Stanley parable? It really got me laughing how much it jokes about sequels.

Mitchmanix has a whole channel playing through comedy games.

One of my personal favourites is The Deadly Tower of Monsters.

I haven't got very far into it, but Rustler is a pretty funny top down view GTA spoof.

West of Loathing and Shadows over Loathing are two really funny and silly games.

Deadpool the game is super funny if you can get it. There is no legal way to get it.

"There is no game"