I have updated my views on the essential sound cards and present to you as efficient a list as I can for your perusal:
MIF-IPC (+ MPU-401)
This is not a "sound card" per se because it really only transmits midi signals. However, it can connect to a vast array of midi modules, and that makes it valuable. While the interface cards designed for it limit you to using only one with a computer, you can also use it in non-PCs and with multiple PCs if each has an interface card inside it. It can connect to an MT-32 or a CM-32L, fully supporting games that use those modules or the Roland LAPC-I sound card. It can also connect to an CM-300 or an SC-55ST at the same time (2xmidi out), eliminating any need for the Roland SCC-1, SCB-55 or SCP-55 sound cards. Connect it to a Yamaha FB-01 and your need for an IBM Music Feature Adapter (at least for Sierra games, the only games that ever supported it) ceases. On the same lines, connect it to a Yamaha MU-10XG and you can sell your DB-50XG, PCC-10XG and SW60XG.
Game Blaster
While you can upgrade a Sound Blaster to support the chips this card uses for sound, some games may require the Game Blaster card to work. It has a custom IC that the Sound Blasters do not. I don't know whether any game requires it, but Creative's demo software might. Also, some games default to Adlib and can detect the Adlib chip on the Sound Blaster.
Sound Blaster Pro 1.0
The Sound Blaster Pro 1.0 is fully and 100% downwards compatible with the Sound Blaster 1.0/1.5 and 2.0. The Sound Blaster Pro 2.0 is not as compatible only for the simple fact that games supported the dual-OPL2 arrangement in the Pro 1.0. The OPL3 arrangement of the Pro 2.0 is programmed differently to support stereo FM sound. Games supported the dual OPL2 setup for additional voices and stereo music. Gameport should be OK with slower machines.
Sound Blaster 16 CT-1740
If you need 16-bit digital output, this is your best bet. Stick with this model and its companions the CT-1750 and CT-1770, as they are only real 16s with real OPL3 chips. Later 16's usually boast of Creative's QMS synthesis or the inferior Vibra chipset. This card is necessary if the game is using 16-bit digital samples. Also comes with a waveblaster header for a daughtercard. Good as a UART midi interface with a V4.05DSP.
Sound Blaster AWE64 Gold
If you value the AWE wavetable synthesis, then this card is for you. It uses Creative's Quadangular Synthesis, a supposedly superior method to Yamaha's FM Synthesis. It has SPDIF support for everything. It contains 4MB of RAM, more than enough for any game. Gold plated RCA outputs and the best signal to noise ratio. You lose the waveblaster header, but with a DSP of 4.13 or higher, it is worth it. Not a full length card, unlike the AWE32s.
Gravis Ultrasound Ace
If you need an Ultrasound for games, why not use an Ace? It contains all the playback capabilities of the Classic and the MAX. It does not record in 16-bit, but you aren't using this computer for recording. May be a bit tricky to upgrade to 1MB. A great support module to the Sound Blaster and it doesn't take up a full-length slot.