A 3D HD Pokemon game, possibly an MMO, or at least with a hugely comprehensive multiplayer component. I want a fully realized pokemon world goddamnit. I wanna see pokemon roaming around in the bushing and be able to go after them.
A proper pirate Action-RPG game. I even have a story in mind for it, your the first mate on a sucessful pirate ship, but your wild adventures have increased your notoriety on the high seas. Next thing you know, your ship has been attacked and everyone including your best friend, the ships captain, has been killed. Only you survive, and its up to you to assemble your own pirate ship and crew and take revenge on the pirates who tried to kill you. If Rockstar and Bioware could work on that together that would be great.
A proper modern day rpg. Haven't really thought this one through as much, but its still a bit of an untapped market.
A game set in Ireland, that would be badass, set it during the Easter rising of 1916, or in the war torn streets up north. It could happen.