Give me the tools to make my own game that my friends and I could play. A "game" that takes what Second Life and Minecraft both have; the ability for us to create our own story and share it with friends with an easy to use interface to create in.
A game (editor) that gives us the ability to modify the landscape, texture objects, make objects, animate basic movements, put events in, even record our own own dialogue and have it linked to characters/NPCs in the game.
Something where when we're done making it, we can post it somewhere, have other people download it and either play it or connect to our hosted server to play it with other players.
Sell a client and creator versions (client can only download and play what's made, editor has the ability to act like a client and in addtion allows you to make the game world).
This is the one thing that those games that surprised everyone did that nobody seems to understand yet. They gave you the ability to create what was in your imagination and then share it with others to enjoy.
If I could create a world as detailed as the Skyrim world with the easy-to-use interface like Second Life has, have my friends log on and play it with me like we can in Minecraft, and be able to record voices and create stories like the dialogues in SWTOR, I would buy the game in a heartbeat.
Additionally (and this is pushing it I know), if I could take the worlds I make, and have the opportunity to sell (or allow download for free) them in some kind of developer moderated marketplace, even if a developer takes a cut of my profits, I would pay any price for that, because the game would always be changing, people would get to tell their stories, show their worlds, and it would be always changing.
This is obviously a basic idea that needs a lot of development, but I've been waiting for SOMEONE to do it. You have hundreds of thousands of people who play D&D in groups, making their own adventures and games. As we grow up, we move, we change, but we all remember those wonderful adventures. Give us a way to play more online with one another. A new way to create and play an RPG game.
p.s. don't impliment voicechat, no need to recreate the wheel when there's so many clients already out there that do that.