You're probably one of very few people I've seen that doesn't think being a Gary Stu is a bad thing, that's fine but personally if I start calling Gary Stu's good then where does that leave actual well written characters? What do I call them? The whole concept of good writing loses meaning, for example if someone who puts barely any depth into a character is considered just as good as someone who does go to a lot of effort to add depth to them than what's even the point of good writing.
My friend, you realize we're not professional writers and critics right?
We're normal everday people that consume these stories because we like them for entertainment.
So, if there's a character or a thing that we like inside a story, that thing is "great" for us, it doesn't matter how simple or complex that thing is, it's still a great thing for us. For example, i like both Naruto and Bleach, do they have problems? of course! i still think they are great stories. So what if there's amazing stories better writen out there, if i don't feel the same about them?
People have this thing were they don't wanna "look / sound" dumb because they like something, so they say "i like it, but i know it isn't great".
To me that's just low-self esteem.
If i like something in the story i'm gonna say it's great.
i like Zoro, he is my favorite in One Piece, i'm gonna say he is a great character, i don't give a fuck if other people want to tell me he isn't greatly writen or some shit, it doesn't matter, why should i care if someone tells me a character is written perfectly if i simply don't like the character he is talking about?
Sometimes it lines up, the thing you like is very well done (for me it's stuff like Breaking Bad, Better Call Saul, Mr. Robot, Vikings and so on).
But theres other times where i like things people don't consider good, like Naruto, Bleach, Marvel Cinematic Universe, i still consider these things great because i like them, it's that simple.
Entertainment and the joy we get out of it is subjective, it doesn't need to be an objetive thing lol.