a simulator with enough realism to make it the biggest most realistic simulator in the world with mixtures of puzzle, action, adventure, simulation, strategy, and etc in various areas. game would also need extreme customization, such as reading your thoughts and generating outfits based on your thoughts fantastic ways to customize
a 3d haircut system with varied tools to mix physics with character customization, a vast database of outfits which you can look up and give different colors/textures to (see the sims 3) various options to create a new house, possibly more than there should be. there would have to be over 10,000 different jobs available with a sort of simulation and various customizable things you could do.
and various areas where you would have to combat other players and/or npcs (i didn't mention how there was an option to play online?!) and various areas of realism. there would be various settings for speed/timescale, preferably a number like as /timescale, every npc that should exist would exist, events would be as likely to happen as they should be, more or less
you could choose from different eras to play in, and the game would have very realistic graphics and sounds, and the soundtrack would be made by hans zimmer
i am done