Does it matter? When Ferrari signed Michael, they were one of the worst teams on the grid who were dumped by the likes of Mansell and Prost. The only goal that Ferrari had, was to win a championship and the only top guy who accepted the offer, was Michael. It was because of his influence was that, Brawn and Byrne joined Ferrari. Once the core was set, there was only one goal and that was to win driver's championship as Ferrari never prioritized constructor's championship so there was never a need to pair him with another champion. That craziness was well deserved by Ron Dennis, who was the reason why Lewis got champion team mates. Did he beat all of them to distinguish himself apart? You know the answer.
Would Lewis have left a team where he would have won back to back titles and had the audacity to go to a struggling team?
He left McLaren out of frustration of not being able to win another championship, just like Senna left. When Lewis switched to Mercedes, Nico was a nobody and it was purely because of Mercedes' rules of engagement which made Nico looked as competitive as he appeared and it was primarily because of Lewis' reliability nightmare due to which Nico could win that championship. Lewis was lucky that Brawn had already prepared the team for an upcoming domination.
Link -> Hamilton 'rolled his eyes' at Mercedes option - Ecclestone
Couldn't Michael have beaten another champion as his team mate? Anybody's guess. Is that a yard stick to measure his talent, absolutely NO. Will that make him any lesser of a legend than Lewis, hell NO.But with the Red Bull door closed to Hamilton, Ecclestone revealed he personally advised the highly rated British driver to consider Mercedes.
"Why not talk to Mercedes, Lewis?" he recalls saying.
"Lewis rolled his eyes ... but I told him that he had nothing to lose as he wanted out of McLaren," said Ecclestone.