Imagine the film made in the 1940s with Orson Welles in DiCaprio's role and Joseph Cotten in Joseph Gordon-Leavitt's.
Then imagine Harry Cohn sitting in the Columbia screening room, ass twitching away1 as the lights come up, bellowing "What the hell was that?!" through the cigar smoke.
I'm not saying that Christopher Nolan is this generation's Orson Welles or any other generation's for that matter, but I kept picking up on these feelings about the film. Something about DiCaprio's look was very much like Welles. Maybe it's the facial structure. It definitely wasn't his acting, and the more I thought about the Welles connection the more I wanted DiCaprio to act more like Welles dagnabbit. He did fine, to be perfectly honest, but he wasn't what I kept expecting him to be. (Similarly, I wanted Joseph Gordon-Leavitt to lay off the Edward-Norton-meets-Keanu-Reeves schtick, but liked his character well enough anyway.)
The real Welles connection comes in the presentation. The film (unexpectedly, if you go in without much warning) hits us hard and quickly with some pretty heavy concepts, and gives us enough explanation without spoon-feeding us so that we may think about it and discuss it later. I'd like to think that's what Orson wanted his Mercury Theatre to achieve. To present you with something very challenging yet manage to engage you, entertain you, and then reward you for thinking.
I don't think the actual story would've been the same. The real serious science-fiction was still all on paper (and in Welles' case the radio) and I'm not sure if mainstream audiences would have been ready back then for a story like Inception's with complex concepts and theories about dreams and variable length timelines.
However, Welles loved timelines and messing with the linear, so it's quite possible to imagine that had he been allowed to continue and further his cinematic career successfully (had Hearst not held a grudge, had The Magnificent Ambersons not been cut, if It's All True had been finished...) he might have come up with a simplified version of this story. Or at least one involving multiple interconnected timelines all intercut.
I could see it happening.
Pretty good movie as far as I was concerned, anyway, even though I kept wanting DiCaprio to be Welles.
1. Harry Cohn was the head of Columbia Pictures and one of the meanest cusses to ever run a studio. When he died, so many people attended his funeral that Red Skelton quipped "It proves what Harry always said: Give the public what they want and they'll come out for it."
One time while Cohn was eating in the executive room at the Paramount commissary, he described his formula for determining a successful film: the film was bad if, while screening it, his fanny squirmed. (His word choice, fanny.) If his fanny didn't squirm, the film was good. This caused screenwriter Herman Mankiewicz, who'd already been banned from the executive room a few times, to remark "Imagine that -- the whole world wired to Harry Cohn's ass!"
Mankiewicz cleared out his desk later that afternoon.