Lots of silly reviews
These are MIDI files, they don't contain any information about how the instruments should sound, they contain only the equivalent of a musical score.
If you want it to sound like a DOS computer from 1982, then you'll need to download a special midi player made to sound that way - most people, most of the time want their MIDI files to sound like an expensive synthesizer module with realistic sounding instruments.
Here's a link to an OPL emulator for Windows... https://vgmrips.net/fo%22midi%20files%20from%20Enemy%20unknown%22%20(by%20povelitel,%2025%20Aug%202004)%20[8/10]%20This%20is%20very%20rare%20files,%20I've%20searched%20many%20sights%20until%20fourum/viewtopic.php?f=15&t=1935
Contrary to one of the other reviews, emulating an FM synthesizer is absurdly easy for any modern computer, FM synthesizers are not "analog" and are based on simple sine waves created by very cheap microchips, playing a sample is orders of magnitude harder.
The reason your MIDIs sound different is because the midi player is trying it's best to make them sound GOOD using modern samples and high quality resampling algorithms to try to make sure that saxophone really sounds like a saxophone.
Then some addled brain reminiscing about the worst synthesizers in the world complains because it doesn't sound like a 1980 Casiotone.