Have you played 'Vampire: Bloodlines'?
It's done entirely in the theme they build, but there is darkly camp stuff all over it. Especially if you play the Malkavian. Especially then.
Have you played Mass Effect 3 and the Citadel DLC? Almost nothing changes from the rest of the game except the situations they're in are comedic, and Shepherd plays the straight-man (or woman) and there's very light glancing at the fourth wall and it is the best DLC I've ever played because it's hilarious. But it's never not Mass Effect.
I think that a major problem is that most of us who RP are not writers and therefore don't have the talent or practice on doing things that are more subtle than engage whatever whimsy hits their mind at the moment. Many times, we all play whatever theme we want. We can only hope that we all play it close enough to the one established for the game.