I'm still waiting for the game I imagined back when I was a teenager.
I want a game where I can pilot a space ship, it takes place in a persistent universe, and has a high resolution terrain. I'm running from some big battleship in my freighter. I drop in towards a planet, heat shields blazing. My ship is shuddering from the occasional laser blasts from the pursuing ship, and just before I drop below a cloud layer, I drop a nuclear mine that detonates a few seconds later. As it does, I take the my ship down, come to an emergency stop above the water, and cut all power. By the time the fireball and radiation above fades (it hasn't hurt my pursuer, just jammed his sensors), my ship has sunk underwater. Without a power signature, as far as the other guy can tell, I've either somehow jumped to hyperspace, gone stealth, or was the explosion he just saw. If he's suspicious, he can bombard the ocean, but how effective would that be?
Or... I've made a homebase on a jungle planet. Using phasers or lasers or whatnot I've hollowed out a cave in a cliff face where I can park my ship. Same thing in asteroids, moons, etc.
Fleet space battles, from big ships to little. Carrying crew that can walk around in the ship and do repairs and man weapons. Have a couple of fighter sleds in the hangar that can be deployed by living players, etc etc etc.
Some day...