This is a lot of fun to think about Here's my criteria for my 'ideal' game:
MOST IMPORTANT: A game that isn't clear-cut from the start. Not necessarily a genre-shift, but something where you don't actually know what will happen, or who will end up together. For example, there is the possibility of a yaoi route, or of two of the heroines falling for each other, or of the protagonist dying halfway through - nothing is off limits!
Genre should be horror, mystery, psychological, utsuge or nakige.
Not too much comedy, and nothing slapstick.
Relationships develop believably.
No childish, deredere characters.
No loser protagonists, please.
It's probably too much to ask, but more believable H-scene voice acting where the girl doesn't sound like a cross between a baby and a strangled cat.
Beauuuutiful artwork with detailed backgrounds.
YANDERE YANDERE YANDERE