I was introduced to Star Control 2 by way of the Ur-Quan Masters - a free remake made possible when the original creators released the source code into the open-source community.
It's an epic space adventure / strategy / arcade game. Hard to define, in fact, because it does so many things so well. It's completely open-ended, presenting the player with a galaxy to explore and exploit, technologies to acquire and use, alien races to contact and communicate with (sometimes with hilarious results - the script for SC2 is among the best I've ever seen in a game), forge allegiances, make war, engage in ship-to-ship combat... there's so much to do it's mind-boggling.
Being a space game it doesn't have to do much to appeal to me visually, and while it's quite basic compared to modern efforts it still has a very attractive, bright and colourful VGA style. The atmosphere is helped no end by some excellent music and ambience.
The short end of it is that Star Control 2 is comprised of several types and facets of gaming that I am a complete sucker for. There are trading games, combat games, exploration games, strategy games, even diplomacy games that I've enjoyed, but this one takes all those things and mixes them together in one glorious package. Some games you play for a quick fix, and others you settle down with for years. Star Control 2 is firmly and permanently in the latter camp.