Space Rangers 2 is a thoroughly enjoyable 2D space "sim" that takes place in a dynamic universe.
Dominiators, or machine aliens are invading the known universe and it is your ultimate goal to help the races stop them. The game is semi-turn-based in that real-time is broken into segments where you decide what to do.
There are many aspects of gameplay to this game. For example, to make money, you can go on these text-based quests on different planets where you are given a story and a list of choices to make. You must solve the quest by making the right choices and are rewarded upon its completion.
You can also hunt pirates which are quite intelligent in their decision making and will often land on planets to repair when they are about to be blown away. You can trade goods with planets posting the right prices but you are also competing with other traders since prices will change during trades.
There are black holes where if you fall in you play an arcade style shoot-em up game and are rewarded if you survive.
The universe is vast and dynamic with, of course, many races with their own feelings towards you. Dominators will raid systems and take over planets. The alliance ships will call for help in defending these planets and will organize to free planets that have been conquered. All the while you are free to join in if you feel the call of duty.
One of the most fun games I have ever played. This is a game where the gameplay is done right. The only downside of course is the 2D graphics which I suspect give the developers more freedom and room to focus on gameplay. The switch over to 3D 14 years ago has severely choked the creativity of gameplay in games.