He's given the credit for Batman's creation because of a contract he signed with DC that gave him sole credit for it, along with all the bonuses that came with it. He came up with the initial concept, true, and the character design, and his artwork was a big help in establishing the overall look and feel of the character, but most of the really important stuff - a number of the villains, the detective aspect, the origin, etc. - can be attributed to Bill Finger, the initial writer and co-creator. Bob Kane certainly had talent as an artist, and he deserves his share of credit, but overall, the guy's always struck me as a bit of an egotistical glory-hog.