He is the world's greatest detective.
That's actually one of his titles. He didn't give that name to himself, y'know. He was even introduced to the world in an issue of "Detective Comics!" Who else even comes close?
C’mon. Sherlock Holmes maybe, but few people would declare him a hands-down winner. When it comes to intelligence, problem solving, and overall crime detection, who else are you going to compare the goddamned Batman to?