A few:
Ghostbusters: The Game, Evil Genius, Dragon Age Origins:
I would love a game that had gameplay like the Ghostbusters game did, but also a kind of management / free roam style, where we build our own Ghostbusters franchise around the world, take on the missions we want and generally just do what we want. That would be so awesome.
Marvel Ultimate Alliance / Infamous / Oblivion:
I would love a free roaming game set in the Marvel Universe that let us create our own/ use an existing character, with as much to do as Oblivion and gameplay like Infamous.
Total War Series, Star Wars: Republic Commando or Battlefront, Command and Conquer Series:
I would love a galactic Star Wars strategy game with battles that had as many units as the Total War games do in a battle, but also let you zoom in and control a soldier, that could play similarly to Republic Commando or Battlefront.