Batman is probably my favorite superhero of all time, and one of the primary reasons is the fact that he is actually just a normal man who has been able to utilize his own resources in order to give himself abilities that others do not have. He does have superior intellect and physical prowess, but much of this was accumulated through years of study and training. Rather than being able to just overpower any of his foes like Superman might, Batman typically out-smarts his foes and uses his superior detective skills.
The story of Bruce Wayne is also one that is tragic and timeless. It is the story of a young boy who witnesses his parents getting killed during a robbery, then grows up wanting to seek justice because this experience. While this might seem to be a stereotypical superhero origin story today, it was something that was completely original when the character was first brought into existence. It could easily be argued that the story of Bruce Wayne is actually one that has become archetypal when it comes to comic book heroes, and that is largely due to the creators of Batman coming up with this story. It is a story that anyone can relate to, particularly if they are a young boy, which was the original target audience of comic books.
While the fact that Bruce Wayne is a billionaire might be something that makes it more difficult to relate to him, the overall story is one that is definitely relatable. The fact that he is simply a man who faced tragedy when he was young and dedicated his life to doing something about it is something that can definitely be an inspiration to a lot of kids, as Wayne was not born with powers, but he developed skills.