Terry Gilliam's Time Bandits (1981). A classic fantasy film, one of the big unexpected successes in theaters that year, a story that ends in a truly original way, and an experience well-remembered by many, many people:
I was at a friend's today, and doing my now extremely occasional video game playing -- Dead Or Alive 4, where occasionally I actually won fights -- and as another guy visiting was customizing a character to play as, his character reminded me of the giant who walks out of the fantasy-world ocean in that film.
(That was the first work of Gilliam's I ever saw as a kid, pre-dating my first exposure to proper Monty Python. The giant not seeming to care that it had a boat on its head, and its being completely oblivious as it stepped on the house with a troll family in it; that was my kind of perverse, even when I was 9.)
I could then picture it: a game where you play a kid who falls in (almost literally) with the Time Bandits as they fall through holes in time. They'll experience, well, skewed versions of history. (I do already know, f'r'nstance, that Napoleon really wasn't as short as we think he was. More medium-height, as this Kate Beaton cartoon so helpfully demonstrates.) So much room for environments that programmers could create, and for players to explore; it could work as an online shared-world in an MMORPG, too. Then there's the Time of Legends, which would allow for even greater flights of fancy in creating its world; so much which programmers could expand on. (Gilliam himself could, perhaps, design ideas for more of the world. Hire him!)
And c'mon, the ultimate boss would be Ultimate Evil? How cool would that be? And perhaps near-unstoppable, but I'd leave it to the more strategy-minded video game players to figure out HOW to stop Evil.
A part of me will always hope for an Adventures of Baron Munchausen video game, too, but as much as I seriously love that film, it's too niche for such treatment. But Time Bandits: The Game? I can't be the only one who can picture that happening.