Best Girl Syndrome

Best girl syndrome is when someone feverishly believes that their favourite character in fiction (typically a female in anime, hence the name) is the best character and will be stubborn in saying that theirs is the best and everyone should like it, and that if they don't they simply say that they know them better and say that the other person is in denial, not considering the fact that other people have different opinions.

Guy 1: god I love insert anime waifu here
Guy 2: nah is insert different anime waifu is better.
Guy 1: fair enough, I just like mine better.
Guy 2: you don't seem to get it, they are better.
Guy 1: ...to you maybe, but I still prefer anime waifu1.

Guy 2: you just aren't giving them a chance! Stop being stubborn about it!
Guy 1: and you have Best Girl Syndrome