For me, it's C&C Generals. It's one of the, if not the worst entry into the C&C franchise.
The only people who like it are people who are nostalgic for it and arabs.
As a "so bad it's good" game? Shadow the Hedgehog. Loved it as a kid, but I love it as an adult for entirely different reasons. So many memeable lines and moments, so little time.
MySims. It's an unpolished, unstable slagheap of a shovelware title from one of the most morally bankrupt publishers in the known world, but I still enjoyed every moment of it. It's a pretty chill game, and there's an oddly satisfying feeling from making stuff for the characters in it.
Compile Heart games- the one name most people may recognize is Hyperdimension Neptunia- are a company known in Japan as making "shitty games". Except I absolutely love their games for some dumb reason. Neptunia especially in their video game industry parody!
I like to pop Hard Drivin into my Sega Genesis once in awhile. Its not a bad game but it horribly aged game with single digit frame rate. Its a weird game to chill out to and considering it uses the Genesis hardware without any advance chips for the polygons its impressive.
I guess you can apply 75% of the N64 library in that category as well.
Does DmC: DMC qualify? The writing is atrocious and the attempt at rebooting a cheesy over-the-top action series into a dumb "satire" on Western culture is laughable. The characters are all horrible and nowhere near the likability of the original series characters. That being said, I kinda like the soundtrack and the combat mechanics, while woefully unpolished compared to the classic series, has a few good ideas like how it handles weapon switching. When the combat is at its best, it can be decently fun, though the game loves to toss in bullshit like color-coded enemies and big annoying fucks that don't flinch from your attacks. The Definitive version does address a few issues though such as adding a lock-on and allowing you to attack color-coded enemies without then necessary weapon (although they don't stagger).
I can squeeze some enjoyment out of it, but if I had to choose I'd pick DMC3, 4, and now 5 over it.
Sonic R. Yes, really. I used to think this game played like a bucket of horse assholes, but once I realized you're supposed to control your racer as if it were a car (i.e. drifting and strategic braking are important) I suddenly found myself liking it a lot more. It's the only Sonic-branded racing game where they don't arbitrarily stick you in a vehicle, and the combination of racing and platforming is actually very satisfying. And of course, the music is unforgettable in all the wrong ways.
However, it is definitely not a good game. The controls are very unintuitive for platforming, the game is insanely short with only 5 tracks, and the graphics look like the Money For Nothing video shat itself. As a party racer it doesn't hold a candle to something like Mario Kart, but I appreciate its uniqueness and I think Traveller's Tales could've taken it a lot further.