I don't like them. All the parody games i have found either changes the tone of the source material too much or changes the characters too much in both personality and body. Just like this recent parody of The Last of Us i found they took little ellie and turned her into a big busty adult whore who acts nothing like the character from the game.
Some of the smarter Devs us the "Parody" exception to bypass copyright laws. Most devs don't know about that. They create games based on a personal desire to either fix what they feel is broken, or turn a particular character into a cum dumpster. The vagaries of author self insertion apply. Most parodies are just nerds trying too hard. PastryIRL and the Cathornero team are doing a good job with Adventurer Trainer and Lewdest House respectively, but that's it. Everything else sucks. Look at the F&R (Fight and Rape) clicker games. Just crap. You press a single button to turn any game/anime/comic character into a floppy, braindead sextoy.
tl;dr Mostly crap, the good ones are smart devs who onow the audience and the legalities.
Normally I do not like them. There are rare time where they work. If the characters are very interesting or attractive. Parody also shouldn't radically alter story I think.