To use other Nolan movies as a point of comparison, Memento and The Prestige are much more accomplished in terms of fully exploiting their concepts. And within the domain of movies exploring the theme of "your lived experience is a dream/illusion", there are much more effective and/or complex examples[1].
I have a feeling that Inception is kind of like Interstellar in terms of public perception: people are psyched by the initial concept, so they don't pay attention to the fact that its underlying narrative structure is pretty run-of-the-mill.
I guess I sound like a buzzkill! If I've missed any deep concept within Inception, I'd be glad to be schooled/enlightened, since I like understanding what makes a movie tick. Also, I don't think it's a bad movie at all, just that it's not that complicated once we're past the initial disorientation.
[1] Before anybody asks, in no particular orders: In The Mouth Of Madness, Mulholland Drive, Paprika, Written By. In a different vein: Eternal Sunshine of the Spotless Mind. Hell, even Total Recall (1990 version) and The Matrix probably apply.