This is a very open question and I don't think there is a perfect concept, mainly because we all have different opinions about the right game and because space shooters are 100% fictitious.

The one space shooter that I have in very good memory is of course the Star Wars: X-Wing series.
Since then I haven't really played any other that would have come close to that experience (good memories are hard to live up to, I know). What I liked about those was that you would fight on one side of two armys (not just against pirates by yourself), but you would only get a goal for the mission and then be completely free to move around. I think when we decide to play a space game we expect to have alot of freedom in terms of movement but also on how to manage our ship as in shields and energy managment.

So I think that overall feeling has to be right, otherwhise space shooters can easaly get boring, because you can't add much content, dockfighting has to be interesting by itself.

Ou right, Freelancer was one other space game that I really liked...

so long...