There is no simple answer for this. A lot of it comes down to what the game's soundtrack was composed for and the level of care put into composing for different audio options. Some games even have different sound tracks depending on the audio source used.
In general, I prefer General MIDI and MT-32 composed sound tracks to their FM equivalents, but it does depend on the game. There are also cases like X-COM that support both, but sound better on an MT-32 in my opinion (best on a CM-series module with the extra sound effects).
I also wouldn't lump all Sound Blasters together, since there can be a noticeable difference between 8-bit sound and 16-bit sound in games that properly support the latter.
There are also things like low-pass filters used on older Sound Blaster Pro cards that removes some of the high frequency hiss associated with 8-bit samples in older games. This can make certain sound cards preferred for older games compared to sound cards that lack low pass filtering.
There are different flavors of FM output that can lead to audible differences. For example, FM playback on the Adlib Gold (and Goldlib) sound cards is difference (and imho superior) to playback on other FM/OPL supported sound cards.
Personal preference also plays a big role. There are some games that have arguably superior quality sound tracks composed for certain devices. For example, Deathtrack has an elaborate MT-32 music score. But I actually find Deathtrack's MT-32 music overbearing and prefer playing the game with Adlib sound. Similarly, Star Control's MT-32 support results in instrument sounds being used for sound effects which just sounds weird and bad. So I prefer Adlib for Star Control as well.
You also have cases with poor implementations of certain sound standards. For example, the Gravis Ultrasound support in the Crusader games is stuck on mono playback. 16-bit SoundBlaster support is the superior option for those games. In contrast, the native hardware GUS support in games like Epic Pinball and Jazz Jackrabbit means these games sound and perform better with a GUS than a Sound Blaster.
More often than not, I take things on a case-by-case basis. I'll try different options and stick with whatever I like best.