WingCommander : First video game series I ever played on my PC. Great games, I loved those interactive movies. You don't get things like that anymore ...
Tachyon : Great too. Excellent story, great dialogues, much action + ship customization (which I love ^^ ).
Back to topic : Nexus is one of those rare games, that are really tactical, and don't just make you rush at your opponent. You only had a handfull of ships, carefully picked and equipped, and when you lost one, it really hurt. You couldn't just throw cruisers at the enemy until he went down like in Startrek Armada and such.
But as so many cool unusual gaming concepts, people didn't really accept it. They all want a base, some mining vessels and a battleship rush in the end. Same thing happened to Ground Control which was the greatest RTS series I ever played. Starcraft couldn't lick the dirt off Ground Control 2's shoes when it comes to tactics. But it had no base building, so it didn't sell very often -.-