Even though I think it's obvious, I am going to start off by stating there is no comparison going to be made between Christopher Nolan's Inception and Edgar Wright's Scott Pilgrim vs. The World in this post. What I want to talk about is each films use of alternate filmic reality's or more specifically making a reality unto itself. Furthermore I want to suggest that these alternate realities are why both these films are outstanding and and how they work successfully in the film.
As I said, what works so successfully in these films are that the worlds in which out protagonists inhabit is entirely alternate to the reality in which we know and live in outside of the theatre.
SPOILERS BELOW: Stop reading if you don't want to have the film SPOILED for you.
Overall both films are great! Each film plays to each of their audiences expectations and deliver. They suspend their beliefs and allows their audiences to wade within an alternate reality where all is wonder and awe. Allowing for a great moviegoing experience. Hope you have a chance to see the films! If you're a film lover they're something to see even if you don't have much interest in the subject matter.