So I was thinking about this tonight while I was re-watching Sam Raimi's Spider-Man. With just a few minor edits Spider-Man could have been the first film in the Marvel Cinematic Universe instead of Iron Man. Here's how i think it could have worked.
So at the beginning of the movie we have Norman Osborn presenting his Performance Enhancing compound to the Board of directors and some Military Personnel. Now, the first thing I would change is to call the "Performance Enhancing Compound" what it really is... A Super Soldier Formula (Giving us a Tie-in with Captain America). Meanwhile he's also presenting the Goblin Armor and Glider (which the General has already seen). Now everything here stays pretty much on script with Osborn's formula being unstable and the General talking about how he has another option lined up with one of Osborn's Competitors. This is where i deviate slightly from the movie by changing out one General for one a little more familiar to the MCU
Instead of General Slocum (pictured Left) I would use General Thaddeus "Thunderbolt" Ross (Pictured Right). Ross is pressuring Osborn to produce the Super Soldier formula. Obviously this ties us in to "the Incredible Hulk" (We'll just Ignore Ang Lee's Hulk). Ross tells Osborn that if his Super Soldier Formula hasn't advanced to Human testing in 2 weeks...he's going to give the military contract to Tony Stark, who is working on an Exoskeleton (and now we've tied in Iron Man...as well as providing the relationship between Ross and Stark that is hinted at at the end of The Incredible Hulk). The movie can proceed as normal from there with exception that Ross doesn't get blown up in the explosion when Goblin sabotages the Exoskeleton trial like Slocum did. Ross sends a representative in his place. Aside from that, the movie will pretty much proceed as is except for the customary "After the Credits" scene. It deals with Ross being informed that after the attack on the Exoskeleton Stark has shelved the project and Ross is left looking for a new direction for his Super Soldier Project. He reaches for a folder on his desk. On the top of the first page the name "Dr. Bruce Banner" is clearly readable.
Anyway, That was what I was thinking...In the end you get mostly the same Spider-Man movie we all remember...but in this scenario...Spider-Man gets to be in The Avengers. Also, Marvel has control over the movie franchise so maybe Spider-man 3 doesn't end up as the abysmal train wreck it is.