I want a 3D adventure game with a haunting atmosphere.
I say "haunting" because the original was Metroid's 'twin' and the original Metroid had haunting atmosphere out the wazoo, which in turn led to the haunting atmosphere of Metroid 2, the sublime beauty of Super Metroid and of course, the almost creepy feeling of total isolation that you get in the Metroid Prime series.
I got always the same sort of vibe from Kid Icarus, but rather than being entirely alone in the bowels of an alien world as Samus was, Pit seemed to have been traversing the bowels of Hades in order to climb Mt Olympus (not the actual story, but the inspiration for the Underworld and the Sky Palace is clear). The sky, even once you got to the overworld, was never bright or sunny as it was in Mario or the Kirby games, but rather dark and ominous, much like Metroid.
Perhaps it's just me, but I always pictured Pit shining like Gandalf the White as he walked through the gloomy shadows of the Underworld. I pictured mazes and riddles like in the Greek myths and, unlike Samus who could rely on stealth or ovewhelming firepower when confronted with enemies, I pictured Pit as entirely conspicuous in the gloom and being far more vulnerable, but naturally more agile at the same time.
To be dark and gloomy, a game needn't be violent or have the same atmosphere as God of War. No, Pit has a different feel to him and if Nintendo are good at anything, it's capturing the feeling of a character and delivering them into an atmospheric world. Hell, the ending to LoZ:WW was pretty violent and it did so without breaking the cartoony atmosphere.