Carnage would decimate Riddler in three seconds, and the latter two seconds are Carnage laughing his ass off following said decimation. Dr. Octopus would do just about the same to the Penguin. Batman's villains are not particularly powerful besides Ra's Al'Ghul *can never spell that*, they're just wealthy, brilliant, or scheming.
Oh I see. Bottom line is that Dr. Octopus is on a higher caliber than any of the rest. He's just as smart as Riddler and can figure out his 'riddles' in about two seconds, and though he doesn't have the wealth and connections that Luthor has, if it's a fight, it's no contest. If it's a shopping spree at Macy's, that's different.