My dream game is an RTS. Imagine Age of Empires, but each character is a person with their own personality and wants. They get hungry, happy, sad, have a family, then go off to war or on diplomatic missions. You can build cities on top of the land, or underground, and where you decide to live changes your characters. Underground they mine tunnels and get physically stronger, and better night vision, etc. On top of land they get better farm land, and perform better in the day.
It also has RPG elements where you can design armour, shields, swords, etc, and your characters can get really good at both combat and other professions (blacksmith, baker, candlestick maker). Combat would be more realistic in the sense that they can block attacks, rather than whittle down a health bar. The more training, the better the fighter. I imagine the possibility of a single fighter with loads of training and experience going up against an army and winning.
When you kill an enemy, you can loot their body, take their weapons and armour, and then depending on your skill you can backwards engineer the design and make it your own.
Of course, you don't have to do an all out war. You can sneak into an enemy location, blend in with the crowd, and have your assassin take down people with stealth.
*sigh...* One day... one day...