In no particular order...
The Kree-Skrull War (An Avengers movie? Fantastic Four reboot?)
The invasion of the Dire Wraiths (it spilled into a lot of Marvel titles at the time, but could come with an added bonus: a ROM Space Knight movie!)
Genosha (X-Men 5, perhaps?)
The Ballad of Beta Ray Bill (seems a natural for the third Thor movie)
And, if they finally make some deal in the future that allows them to get all the various properties in one movie, it absolutely has to be...
Secret Wars (Avengers, Spider Man, Fantastic Four, X-Men, and more all in one place... nerdgasm!)