...No, not really, Ozma is the superboss no doubt about it. Sure there is a matter of luck to beat him (although at later levels the luck factor deminishes) he is quite beatable. That's like discluding him because of his difficulty.
Besides, thats like saying, "In order to be a super boss, I must be able to beat you every time!" Ozma is difficult and luck is required to win, a true super boss.