It never says Olorin was the "chief maia". I don't think there was one. It's said, however, that he was the wisest.
Maybe he was equal to Sauron, maybe he wasn't. Since he was an Istari he had limitations. Imagine yourselves stuck in a wooden box. Would you be able to jump, run, swim etc.? I know this has been discussed somewhere. Unfortunately I don't know where, or how to do links.
