Okay, your the second person to ask me this so I'll list of what I think makes a game I'd be interested in:
Colourful locations (I pretty get that problem sorted lol)
Colourful characters (as in personality not colour, although the latter helps)
Characters with a reason, not just put in the game for the sake of it
Secrets, suspense, emotion, flare, sadness, enjoyment etc ...
Choice (I like to feel like I have some choice in the game, influencing events and not just along for the ride)
Interesting, interactive and enjoyable new features
Familiar elements (pokemon, characters, locations, events)
I think there's more but I can't think of them at this moment in time.
Good luck with the game man
-Novus-