My first Prime was Transmetal Primal. Second was RID Prime. My first Megatron was actually Gobots Megatron. I just didn't know he was Megatron for like 15 years. I often used him as "Roller" for RID Prime and I assume he's never really forgiven me.
It's the impression I got after reading Bob Budiansky's pitch due to implication that Autobots and Decepticons have left Cybertron for the very first time and energon apparently being their only fuel. Doesn't seem to me like it was a sequel to anything.