My idea for a great Wii game is to make an RPG (of the JRPG variety) with an epic-like save-the-world story. The RPG will have a very simple look, and will make use of your Mii's.

Your main character will be your Mii, and you can choose several other Mii's to be part of the quest as well. Some may show up as party members, non-playable characters, enemies, and bosses. Perhaps with some customization options, such as a survey at the beginning to kind of determine which Mii's get put into which roles in the game. Your character and party members would be customizable with the weapons, armor, accessories your collect along the journey, and the non-playable characters would basically be your Mii's in their role's costume.

It would have sudo-turn based/real time battles with the attacks mapped to (up - down - left - right) motions of the wii remote (if possible) and combinations of these moves to form special combos. And you can build up a magic spells by pumping the nunchuck and combining it with a special combo move.

Well, I really like this idea, and have other ideas for it too... so maybe I'll post more on it later...