As soon as he died (wish Optimus wuld've offed him) in the first one, my first thouht was Galvatron... then when the Revenge of the Fallen title came out that pretty much confirmed it for me. Megatron was reformed as Galvatron by Unicron (i think) after he died right?
"The Fallen" is the name of an actual character......apparentley he's always engulfed in flames.
He goes way back...from the days of Unicorn, etc