What's Up With the Ending?
All's Well That Ends…Deceptively Well
Let's see…earth safe from the Destroyer? Check. Thor, wiser, humbler and hammer-enabled again? Check. Loki, sucked into whirling space vortex from which there is presumably no escape? Check.
Sounds like a happy ending to us.
Except that Asgard is cut off from the rest of the universe, Jane and Thor don't get to take long walks on the seashore anymore, and Loki is only maybe dead.
For a happy ending, it sure leaves a lot of plot threads open. And once you add that post-credits cookie where Loki is definitely up to no good, suddenly that neat, tidy happy ending looks a whole lot messier.
Setting Up To Get Down
That, of course, is by design. By the time Thor came out, Marvel's Very Impressive Franchise plans were coming to fruition. The first two Iron Man movies were big hits, and Captain America: The First Avenger was getting ready to cement the plan.
Even if Thor had bombed (it didn't), Marvel was still ready to set up The Avengers… and presumably more films beyond that if everything went well (it did). That meant they had to leave a few threads open for later resolution: a villain on the loose and a girlfriend stuck on boring old Earth while our hero broods in shiny happy Asgard.
The filmmakers have to do that without denying us the satisfaction of a happy ending. The ending of Thor strikes the right balance that leaves us satisfied while making us eager for more. The immediate threat is disposed of and our main character is relatively safe…but several notable threads are still in need of tidying up.
That balance was actually Marvel's bread-and-butter long before they got into the ginormous blockbuster business. Comic books always played the cliffhanger card as a way of getting you back into the store next month to purchase the next issue. They had long, involved arcs taking up multiple months, but had to balance that against the fact that bad guys had to be beaten.
By the time Thor rolled around, Marvel had perfected this into an art form, and anyone who knew comics back in the day could spot the give-and-take between leaving 'em happy and making them beg for more here.
Comic Drama
And frankly, there's more to that than just getting us back in theaters for The Avengers (or Thor: The Dark World for that matter). One of the goals of the Marvel Cinematic Universe is to simply transfer the experience of being a comic book fan to the big screen. Old school comic bookies can tell you that special feeling of walking into the shop when the new issues arrived, and that sense of excitement at finding out what was going to happen next.
The MCU aims to do the same thing: construct a huge arc stretching over multiple movies that matches the same feeling as a big arc in comics. The only difference is you're buying a movie ticket once every six months instead of a new issue every four weeks.