What makes a good space game?
Exactly the same things that make any other game a "good" game:
* Well-considered and integrated control systems
* A satisfying variety of actions in which to engage, and good integration between those actions
* Appropriate graphics and audio design
* A robust and well-developed AI that provides a realistic challenge
* for MMOs, appropriate and sufficient tools to support multiplayer interaction in-game
* Well-crafted and optimized code that has been de-bugged and thoroughly tested
* If appropriate, interesting storylines that challenge the player and draw them in
* a "point" to the game that keeps player interest high and makes it all worth while
* an indefinable feeling that somehow the game as a whole is more than just the sum of these parts
* and finally, a development team that understands, values, and listens to their player audience
Extrapolating from all that, assuming the game has a good development team and is well coded etc, the other requirements for my "perfect" space game would be:
* Well crafted and interesting graphics and audio that are either ultra realistic, or else stylized in a valid manner.
* Both first person and in-vehicle gameplay supported in both cases by well-designed HUDs/input systems.
* A good flight and combat model, a good trade system that provides all the required tools to support trading, and an interesting, immersive and challenging exploration system.
* Missions/quests that are obtained through the course of regular play, rather than requiring me meeting specific "mission givers" at specific locations, and which interlock in a way that encourages emergent gameplay and opens new activity paths
* Support for a wide range of "professions" and/or professional traits/perks
* The tools to easily find and communicate with other players, and form guilds that have in-game support
* The ability to own/build property assets that can be used by myself and other players
* A fully integrated and functional economic and political simulation that can evolve over time in response to player actions
So in summary, I want to feel immersed in a universe that is much bigger than me but which I can still effect in some way. I want to be the pilot, not just control the pilot, and I want the whole thing to be a complex, challenging and satisfying experience that make s me feel somehow that there is a reason for me to be playing, other than "just playing".
EDIT - Reading through what I wrote, my perfect space game would be an amalgum of the best features of ED, SC, NMS and X3. Not hard to please, am I? 