At the time I had Creative AWE32 soundcard which had sample based synthesizer onboard, so depending on quality of your General MIDI library (which was pretty much dependent on how much expansion RAM you had on card) you could get some really good sounding MIDI music.
I remember friend of my stopping by for the first time after I bought PC - at the time he had Creative Sound Blaster 16, which was only capable of FM synthesis (not sample based, rather oscillators that frequency modulate each other, Yamaha was pioneer of that tech back in 70s and early 80s, of course their synths sounded much better than SB16) - DOOM sounds like this through it
I believe I had a AWE32 back in the days and it sounded great but midi was replaced by CD audio or full samples on the disk pretty fast. Midi is really one of these forgotten forms of musical art.
Well, as this very example demonstrates, it depended a lot on what kind of General MIDI sound bank was in what hardware - it was good idea at the time when limited space was a big issue, but it was inconsistent from platform to platform, and with PC quite a bit even on the same platform, so it's no wonder it got replaced as soon as it was possible.