Some good questions on the GUS. Some I think I know the answers too...
Is there any other card that can emulate the GUS?
Not that I know of. I had heard there were a few OEM versions of the GUS made, but they were still basically Ultrasounds, just green. There are Ultrasounds that can hardware emulate the Sound Blaster (the Extreme), but not the other way around. Manufacturers didn't seem interested, or perhaps it was too difficult to clone the GF1 chip.
The other answer is... YES! DOSbox. 😊
But... um maybe. Other cards keep getting mentioned here that I've never heard of. An Aztech Sound Galaxy NX Pro16 that can emulate the Disney Sound Source? Neat.
Does the GUS need a 386 ISA PC with 4mb of ram to work with it's "own" games?
Well, Star Control is the uncommon exception and not the rule. While almost all GUS games have some minor "push" to get to work (ranging from running a special sound setup or game executable to even a patch), Star Control 2 is one of the games I've found that seems firmly cemented to the ground. I just flat-out can't figure this one out. You mentioned two more, Dark Legions and Archon Ultra. All three of these games I've had to resort to the Sound Blaster. Epic Pinball I remember having trouble with, but I got it to work after a patch.
But most games aren't that hard, really. Many games work without even a blink (Doom, Descent 2, Dungeon Keeper, Outer Ridge - and come to think of it, I won't want to play these games on a 386).
And nah, I have an Ultrasound Classic in the Soyo P4I845PE ISA, which is a P4 2.8ghz with 1 gig of memory, and it seems to work okay. Probably a portion of older games won't run, but that's the fault of the sheer speed of the machine rather then the GUS, and the good part of the tradeoff is playing the advanced games of the late DOS era in near limitless horsepower (Quakeish games).
The Ultrasound will almost never "save" you... meaning don't expect it to work when the Sound Blaster won't. I thought maybe that would be a good reason for getting one. I learned however that if I couldn't get the Sound Blaster to work in a game, I almost certainly could not get the GUS to work. The single exception to this is a game called Hammer of the Gods. Due to whatever hardware config I have or (probably) the game coding itself, I couldn't get both the music and sound effects to work at the same time with a Sound Blaster (I had to pick one or the other). The GUS allowed me to use both, but this is the only time it came through for me on a game when the Sound Blaster didn't. Demos are another story, however. It's been said before around here, but to paraphrase: If you are into DOS demos and you don't have a GUS, be prepared for a lot of silent movies.
But for the most part, a GUS will let your games sound slightly better than a Sound Blaster if you can get the sound to work at all. The line gets blurry with games with native SB16 or AWE32 support. Often the Sound Blaster will sound better then the GUS in this case, but most of the time it's a toss-up. The true test is if the game has MOD music in it (such as Outer Ridge, Epic Pinball or *sigh* Star Control 2), that's when the GUS shines for sure.
Unless it doesn't work. 😁
A little bit blasphemic - what's the use of the GUS in a retro gaming machine?
A good question! I'm happy to answer that and don't consider it blasphemic even though I love my GUS. It's a mixed bag...
It's CERTAINLY not NECESSARY to have a GUS in your retro machine. Take it off your list if you actually like to PLAY games... the reason is you'll be spending hours and hours tweeking your system and batch files and running sound setups to get it to work when all you are really doing is getting your game to sound (debatably) slightly better.
The exception, once again, is demos... but I don't need to go there again.
So yeah, a GUS is not for you if you don't like encountering and solving audio problems with limited appreciable payoff other than GUS-fandom. If you get a GUS, expect to spend a lot of time installing the bloddy thing, figuring your own ways to tweek config files to get your 2+ cards to coexist, and, of course, messing with game sound setups. You might even risk your relationship with your girlfriend/wife if she starts getting jealous of all the time your spending with your old hardware. 😒
I like to think that a GUS is to old sound hardware what a Voodoo is to old graphics hardware. The mainstream hardware got so good eventually (the AWE, equaliviant to, say, a Geforce) that the essoteric extra features of the Gravis didn't really stand up to the ease and performance of the next generation of common Sound Blasters. But just like early Voodoo games, a handfull of vintage games were at their best with a Gravis. If you are a connisseur and get a kick out of old games at their absolute highest attainable level of quality on vintage hardware and don't mind a lot of trouble-shooting, than a GUS might be for you.
Also, it's kind of fun getting Demos to run as screen-savers on a Dos retro rig. I'm thinking of starting a thread for that. I started doing this just because after disappointments from all those games that didn't work, I was asking myself your very question and finally started wondering "what can a GUS do that a Sound Blaster absolutly cannot that would make this effort worthwhile?".
I hope I didn't rub too many people here the wrong way comparing a GUS to a Voodoo. 😎
Most of the folks here know this already, but I should note also that if you're looking for a serious sound improvement across-the-board for all your games, time would be better spent upgrading your MIDI hardware than finding a GUS. A good MIDI wavetable daughterboard or stand-alone card will make everything that can use it sound undoubtably better, and once it's installed, it has minimal technical glitches and headaches compared to the GUS. The sound of a good MIDI card actually stands a much better chance of impressing the average onlooker as well.
On the other hand, I have yet to find any prod from the Demoscene that uses MIDI. Anyone?
So yeah, Star Control with a GUS. Maybe... someday. 🙄