Realspace 3 is a shoot-em-up game I played I think around 2007-2008. Today it's abandonware, but back then it was $30. A bit pricy for a sequel to a flash game considering 30 dollars went a lot further back then, but it was fun. I played Realspace 1 and 2 a lot as well since they were hosted on Miniclip, especially Realspace 2. I was a kid so the idea that you could be the aliens in this game and actually blow up the Earth was insane to me.
Realspace 3 has you as the humans again, though. You play as an ace fighter piloting a custom ship called the Antaris and try to do your best to fight off the Katuri alien menace and protect the shattered remains of humanity after the destruction of the Earth. There were something like 60 levels, so a hell of a lot of gameplay, and it was pretty fun, except for that one level where you have to prevent the suicide bombers from getting past you, that one sucked cause the map was so big it was really hard and annoying to patrol everything properly.
The only really bad part of the game is the ending, it's so lame. The Antaris pilot just gets stranded in space, cut off from the rest of humanity, and it's ambiguous what the fate of mankind turned out to be. That might sound okay, but trust me, it's a very abrupt ending and not satisfying at all.
If you wanna check it out just hit up some abandonware sites, it's not too difficult a game and I think is well worth the time!