Batman is one of the most popular comic books characters to be created ever. He's human and still one of the best vigilantes and skilled fighters in DC. His intelligence (and also money) is an important part of his crusade against crime too, indeed he's often called “the best detective in the world”.
But is he really such an interesting character?
Sometimes people say “his parents died in front of his eyes when he was a child, he inherited their money and he just started dressing as a bat and beating up loonies”.
That feels like an oversimplification.
His parents dying in front of him is, of course, a pretty big deal, and it's the sort of thing that could drive you incurably insane -- which happened with some of his enemies. Instead, he channeled his darkness and rage to do something good.
Batman isn't a bad character and he has some of the best, most iconic and most beautiful stories DC could own (‘Long Halloween’, ‘Batman: Heart Of Hush’, ‘The Man Who Laughs’ etc).
Is he oversaturated? Definitely. Unnecessary appearances or overpowered skills are what comics readers don't like. He's strong and has incredible abilities, but at the same time, he shouldn't overthrow every metahuman out there.
Sometimes his best stories like “The Dark Knight Returns” are so often brought up that fans get tired of them. A good story remains a good story, but seeing it over and over -even in different representations- will sooner or later get boring.
And when people say “Batman is overrated” they probably also refer to most Batman characters, who get way more attention than most characters in the DC universe do.
It's a known fact that Batman’s villains are very interesting even though most of them are humans. They can be charming, extremely smart, dysfunctional, dark, terrifying but fascinating. But just like with the hero, they are sometimes over used and often find their way into video games, movies or whatever comic series or graphic novel even when it's not necessary.
Batman and his villains aren't bad characters, but comic readers aren't exclusively Batman readers. DC has an incredibly big amount of good characters with huge potential who could make some good entertainment.
All fans want is, not for Batman to be erased from comics, but to remind DC that many other characters exist, too!