Of course he would have existed, he's a being. He's a Gerudo, a male, born once every one-hundred years. Would he have been the Ganondorf that we know him? Probably not. Without the ToP he probably wouldn't have been able to be revived, re-incarnated, escapted from Dark Realm, etc... however, he would have existed in Ocarina of Time. Ganondorf seeks power, and his search for the triforce was simply his path to obtaining the power he sought. Ganondorf the man, would have existed with the same ambitions for power, and in the magical world of Hyrule there would have likely been other means (though not as great) of obtaining power, though he most likely would end up failing due to the efforts of Link, Zelda, and the sages. So the short answer, yeah, he would have existed in OoT, however, most likely would not have appeared in any additional games.