Interesting that you suggest FS2, as I recall FS1 being quite good as well. After playing the whole first game, I pretty quickly tired of the genre before getting very far into FS2. Still, either one is worth a look in my book.
Descent: Freespace IS very good, but Freespace 2 improves upon it in every conceivable way. You can also play the first game in the updated engine for FS2 as well.
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