Tom was never the Don, he was acting Don until Vito recovered, so technically Tom always remained as Vito's consigliere, i.e. "the family's" consigliere. During the illness of Vito I think Tom and Sonny saw themselves in the same boat and more or less as equals, except when Sonny lost his temper and said
Pop had Genco look what I got." You can see them acting more like equals (in the film at least, when Michael first comes up with the idea that he will kill Sol and McCluskey. Also you can see them as equals in the scenes where Tom raise his voice to Sonny. He would never have done that to Vito.

Michael, on the other hand did become "The Godfather." He was Godfather to Michael Rizzi, and presumably others, and was truly the head of the family. In a great deleted scene Sonny's eldest daughter and her fiance come to Michael to get permission to marry. It is one of the few times when we see Michael's warm and playful side when he tells the young man that it is ok to major in fine art, but that he better take some business courses. When the young man tells him he is a trust fund baby Michael accepts this but thn tells him to take some business courses anyway.