My dream game would be an adventure, storytelling platformer game.
The main character would be a nameless girl who goes on a journey to find happiness. She would travel through various places (forests, villages, etc..) and meet different characters (who all have their version of what is true happiness).
It would use hand drawn graphics enchanced with some computer graphics, and would have a calm, relaxing atmosphere.
The target platform is Win/Mac/Linux with keyboard / gamepad controls.