Warning - SPOILERS
So I did some reading today trying to find someone that shared my interpretation of Inception, but I couldn't find one, so I thought I'd go ahead and share it with you.
In short, I believe that Mal was correct about their world being fake, and Cobb was wrong.
When Mal and Cobb went deep into limbo together they lost all sense of reality. When Cobb finally came to the realization that it wasn't real, he convinced Mal using inception.
When they killed themselves, they didn't leave limbo and come back to reality, but instead, they went back to the first stage of the dream.
Cobb though they were back in real life, but Mal had the feeling that they were not. When she killed herself, she left the first stage, and went back to reality. Cobb however, believed that she had left reality, and killed herself, when in fact, he was still dreaming.
This theory is supported by many things. But perhaps the greatest evidence comes at the end, when his top does not stop spinning, and his kids looks exactly the same as the day he left, including the same outfits. This suggests that he is still in a dream, and in fact, never left the dream.
Also, if you look for dream like elements in his "real world" you'll notice things. For instance, how does he get to Africa to look for his "forger?" He steps out of his base of operations in Paris, and then he is suddenly in Africa. He said several times himself that one of the surest ways to tell if you are in a dream, is trying to think of how you got somewhere.
When he is in his apartment in Japan, and he spins his top, it is interrupted by his partner knocking on the door. We don't actually see it stop. Also, it is nighttime out the window, but when they go up to the helicopter, it is daytime.
When he is in the bathroom washing his face with water, and he spins the top, it falls off the counter, but doesn't actually stop spinning on his own.
All these and more suggest that he was always in a dream.
What are your thoughts?
I also have two alternative ideas.
Again, Cobb never reentered reality when he went deep into the dream with Mal. But instead of going back to the first stage of the dream when they killed themselves with the train, they actually went deeper into the dream, deeper into limbo. They went so deep, that they could never escape.
This one is a little different. What if they never got out of Saito's dream? Do you recall that when his partner was training Ariadne on how to build levels, he told her that she should make it a maze, to make it difficult to get out? And that she could create levels that were infinite loops by augmenting reality? Now recall how the movie started? From the ending. Cobb woke up on the shore of Saito's unconsciousness. And then suddenly, he was with a younger Saito. So if the movie starts how the movie ends, then that suggests that Cobb is in one big dream loop, created by someone (perhaps Saito) to keep Cobb going and going without ever realizing something is wrong.
If this is the case, then that means that Saito had elaborate subconscious defenses that ensnared and trapped Cobb, and he was never able to free himself from this botched job.