After Lee / Kirby the best thing to ever happen to Marvel is Chris Claremont. Love his work or hate it, there is no denying that his work on the X-men defined Marvel from the late 70's to the mid 2000's as the X-men went from a single cancelled book to the franchise that dominated comics throughout the 80's and 90's. Even after he left X-men all Marvel and subsequent writers did was rehash his plots and cash in on characters like Wolverine that he made popular. You could argue that over the last 5-6 years Marvel has finally shifted the focus from the X-men to the Avengers but for the 25 years before that it was all X-men thanks to Claremont. Its why Marvel had such sales dominance throughout that time.
I don't think it would have looked much different if Disney did not have bought them. They did Iron Man before Disney, they would have done the Cap and Thor fillms anyway and probably Avengers too although it would have been in greater concert with Paramount.
Agreed, although I'm not sure if Phase 2 would be as aggressive as it seems to be shaping up to be, what with bigger risks like GoTG, Ant-Man, and whatever else they have down the pipe.
But really the best thing about the Disney/Marvel merger is that it's hardly noticeable. Disney saw Marvel Studios had their shit together and was content to just sit back and let the cash roll in.
That being said, I completely agree that losing SSM was a tragedy. It was to Spider-Man as BTAS was to Batman, and that's really the highest praise i can give an animated comic show.