I think it all boils down to your preference over how a film should end. Some people like definitive endings where everything or most of the things are either mapped out or resolved. People like resolution. However, there are some, like myself, who enjoy the ambiguous nature of open endings. Allowing the audience to determine which one was the true ending, and then having limitless discussions over why they think either one is the true ending.
, while I'll try not to be disappointed in you using, basically, a "some people like to be force fed and some people don't" argument against me, I'll ask you to read all my comments again. You should know that I'm not a "force fed" film viewer. But all my comments have been about what kind of ending a film sets itself up for. Sometimes a film sets itself up for an ambiguous ending, and if I feel the film deserves it by going for that kind of flavour the whole time, I love it. But in my comments above, I've discussed why I don't think Inception merits that kind of ending.
I didn't mean to imply that. I'm just saying that with most
people, they don't like ambiguous endings. I wasn't signaling out you in particular, just saying based on your comments it reminded me of my discussion with my friend. I apologize if I implied anything otherwise.
I agree that the film was leading toward a cathartic resolution for Cobb's character, but since the film bled the lines between dream and reality, I don't think it really mattered how Cobb found that catharsis. With so many layers of the dream state, how are we to know when is someone dreaming and when someone isn't? The film could have been intentionally very misleading. There are even some that say the entire film is a dream, and that Ariadne was a projection that was meant to therapeutically help Cobb overcome his grief. While I don't think that theory has a lot of merit, the fact that people are suggesting it would imply that others have doubted the reliability of the film in terms of revealing what is real and what isn't. Mal committed suicide because she thought the "real world" wasn't enough. To her, it was almost like the dream world bled into her reality. It's possible the same happened for Cobb as well.
It's also possible that Cobb had no choice, and even though he thought he was able to wake up himself and Saito, they were either individually or both in limbo for so long that it simply put didn't work. That are a lot of lingering questions that are left unanswered, especially since the ending went by so briskly. You could say it was leading to something ambiguous. Cobb found his emotional catharsis in the dream state, so perhaps it was fitting that he found closure in there as well. Who's to say?