The original Descent runs way too fast for me (the rate at which your ship "bounces" while floating makes it look like an earthquake
) but there is a 3dfx version of that which works perfectly. Descent 2 goes at the same speed as D1 on 320x200 but works great on 640x480; in fact, I just finished playing through all the main missions, the addon missions and some of the user-made expansions for this about a week ago.
By the way, on the topic of old games, I just completed Beneath a Steel Sky (without any walkthroughs
); it had an excellent story and a good bit of humor but the ending seemed somewhat rushed.