I mean, since Roger is the captain, he gets the benefit of the doubt, doesn't he? Xebec's crew didn't work out, because the members all were too strong and too ambitious. And Roger managed to be so strong and ambitious that even Rayleigh was fine with serving under him.
I don't see Luffy edging out when its all said and done
Zoro surpassing Roger is more or less a manga fact at this point.
But I don't think anyone needs to be given a benefit of the doubt, equal is just as good of an option.
Rayleigh doesn't seem the kinda guy to have any interest in Pirate king title, he can become one right now, literally knows where One Piece is.
He simply chose to tag along Roger because he had nothing better to do.