Batman is DC's most popular character, and is also widely considered to have the best rogues gallery at DC Comics, as well as one of the best in comics in general. I believe that's no coincidence, as I'm a firm believer in the saying "A hero is only as good as the villains he fights". Similarly, Spider-Man is Marvel's most popular character and is also widely considered to have the best rogues gallery at Marvel, with Bats and Spidey often being neck-and-neck for the best in comics overall. Do you agree?
Personally, I love Batman's rogues because all of them are unique and very fleshed-out. There's a good mix of superpowered and non-powered individuals, a good mix of backstories and motivations, and a good mix of appearances and personalities.