Everyone thought the same in 2002...
Everyone was mistaken then, because the movie clearly wasn't framed to be episodic in the manner that most CBMs are these days.
Thinking back to all of the Spider-Man bullet points it nailed:
- Origin
- Ben's death
- MJ
- High School
- Harry
- Flash
- Infamous bridge scene
- Goblin; archenemesis, and his subsequent death
The list goes on, but many of these are things that could have(and in some cases, should have) developed over the course of several films, but I think that Raimi & the powers that be wanted to make something of a definitive Spider-Man film. Although I enjoyed the movie, in retrospect they were probably a bit too eager to "cover all their bases", if you will. TASM is obviously trying to correct some of this, and is approaching the franchise in a more episodic manner.
The whole movie was a fairly self-contained story that hit all of the wickets, and although the cast and crew signed on for multi-picture deals, I'd say Spider-Man was initially meant to be a franchise of one-offs as opposed to a long, intricately connected narrative ala LotR.
To address the topic, it's anyone's guess. Truth be told, while it would be cool to see Spidey make cameos in other films, or even team up with other heros in an Avengers pic, he's always been a solid standalone character, so as long as the films are being handled well, I don't particularly care where he ends up. The landscape has changed for the genre in recent years, but I just don't think it's quite to the point where sprawling crossover events and multi-threaded adventures can work. That's all we want out of this anyway, but I don't think the cinematic landscape has room in it for an 'Amazing', 'Spectacular', 'Avenging', 'Scarlet Spider', etc to occupy the box office. Avengers would be fun every 4-5 years or so, but when it's all said and done, it's back to business as usual - one franchise, with one Spider-Man, and one focus.
If Sony manages to get their act together, I'd be content with them and Marvel making nice for cameos and Avengers collaborations.