Lots of other people have given this game in-depth reviews, so I shall simply agree with the rest of them. This game is a lot of fun. You'd think a game where every mission basically amounts to flying around in circles shooting things could get dull after a while, but somehow this one doesn't. That might be because the story is fascinating, or because the missions are just varied enough to make you appreciate the differences between them, or just because blowing stuff up with lasers is fun.
The reason why I don't give this game 5 stars is partly because GOG's rating system doesn't allow me to enter in a 4.5, and because there are a few flaws in the game:
1. Some of the missions towards the end of the campaign seem arbitrarily hard even on the lowest difficulty setting. Moreso if you're the sort of person who is fixated on getting every last medal and achievement.
2. The ambient music isn't strong enough to attract your attention during the intense gameplay. It's not bad music, but it doesn't do anything other than set a mood.
3. Every star system looks the same, except for the nebula in the background which changes color. I like having scenery to admire between dogfights.