Riddler Is Like A Bargain Basement Joker
Unlike the first appearances of the other great Batman villains that have appeared so far - Hugo Strange, The Joker, Catwoman, Clayface - the first appearance of The Riddler really isn't a must-read.
It's not that The Riddler can't be a good character, it's just, in his initial incarnation anyway, he lacks depth. Were he a whiz at puzzles that delighted in matching wits with Batman and the police, that would be great, but as written here, he's more of a con-artist who cheats when he can't solve a puzzle - which makes him seem more like the Joker - willing to 'play from the bottom of the deck'. He's also somewhat homicidal, further encouraging comparisons to the Joker. Put it all together, along with his name, and what could have been another unique addition to Batman's 'Rogue's Gallery', comes off more as a half-baked way to clone the success of The Joker.