Universes are the thing now. You don't have trilogies anymore, you have three separate franchises building up to a crossover (you'll be stunned to find out about some of the properties Hollywood wants to do this with). No franchise is an island anymore... unless it's Spider-Man.
Fans have been clamoring for Spider-Man (and the X-Men and the Fantastic Four) to be able to cross over with the Avengers and all the Marvel Studios heroes. And you know, maybe it could happen - Marvel has already rewritten ALL the rules on how blockbuster movies work. But it won't happen while Avi Arad is running the Spider-Man franchise (into the ground).
Arad spoke to IGN and was asked what it would take to get Spidey to meet up with the Avengers, and the answer was basically Arad's death:
“I think I’m probably a little bit of the militant here. I think it will take a moment in which we’ve run out of ideas. There's so much to tell about Spider-Man. There's so much to tell about the Sinister Six. The relationship between Spider-Man and Venom will bring a whole other world in.”
Arad thinks doing that would be a 'stunt,' as opposed to mining every single character who has ever appeared in a Spider-Man comic for their own franchise (Rocket Racer, coming summer 2020).
“But we really feel very confident that we have so much to do […] Peter Parker is unique; he's really different. He's not an Avenger. He's not an X-Man. He's unique and we revere that. And we'd rather work really hard to have the right ideas than – you know in the toy business we used to make toys glow in the dark when they weren't selling well and it gave at least another Christmas. We don't need it yet.”
You know, I agree that Peter shouldn't be an Avenger. I always hated that status quo in recent Marvel comics. Spider-Man is a loner. That's established in issue 1 of Amazing Spider-Man when he doesn't join the Fantastic Four. I like him that way! But that said he's a great character for bouncing off of other characters, and it's too bad we'll never see Andrew Garfield's Spider-Man quip at Hugh Jackman's Wolverine while Chris Evans' Captain America tells them both to keep their minds on the mission of toppling Doctor Doom.
It's worth noting: I think Avi Arad is the problem with the Spider-Man movies. There are a lot of people to blame for the franchise's descent, but Arad is definitely near the top of the list, if not the very top.