I think that neither the film nor the novel show us that Michael was jealous.
"When Hagen had entered the room Sonny had come rushing to embrace him. Michael realized with a faint twinge of jealousy that in many ways Sonny and Tom Hagen were closer than he himself could ever be to his own brother." - The Godfather, page 96.
Forgive me for bringing back such an old topic, but I've been reading the novel again (it seems like the 100th time) and I got the itch to return to this forum and discuss some of the finer details.