Interesting topic, but don�t forget that the reason Roland introduced the GS sound set was because they wanted to get out of the limitation of 128 voices that General Midi allowed, Yamaha also did the same with there XG sound set.
Creative Labs with their earlier sound cards also supplied the GS sound set that could be loaded and played by the Sound Blaster cards, thus giving a vaster wealth of sounds compared to the Onboard FM synthesis.
The GS sounds also come as standard with Windows Media Player, and you can select them from the Sounds and Audio Devices in Control Panel. (If your computer uses an Onboard Sound Chip then the GS voices are set up by default)
Interestingly the GS sounds are not that well known compared to XG which became the most used standard after GM.

Bill