Just pulled my floppies out and tried these games on DOSBox to see what they sound like on an MT-32, as I only ever heard them on a SB16. I originally bought the games as a combo pack that I found in a bargain bin for $10-20 (they were at least a few years old at the time) Looking back on them, I have no idea how I managed to beat both of them - I must have been really bored at the time (in fact, I remember it was winter when I was playing the first one, so maybe that explains it).
The first game was terrible. Almost no music, poor sound effects, disorganized levels that almost felt like they were designing and developing the game at the same time. Wort of all, the game didn't feel very alive - there was no atmosphere. You just ran around trying not to get lost while you killed stuff and got killed. The graphics were decent, mostly because they were colorful 256-color VGA. Looked like they were made in DeluxePaint II though...
The second game was much better, despite using the same engine. The music was the best part: it has some of the best music I've heard in a PC RPG, and the songs fit the mood of what was happening in the story. The music really took advantage of the stereo capabilities of the SBPro/16's OPL chips which also impressed me because most games didn't take advantage of anything higher than the original, monophonic OPL2 in the Adlib/SB.
The second game also had a much stronger sense of story and purpose that pulled the player in. A unique feature that I've seen in very few games is that it would occasionally switch to one of at least 3 separate parties under the player's control, so you were playing at least 3 separate plotlines at once (Frodo & Sam, Merry & Pippin, Aragorn & Legolas & Gimli). Still, the graphics, interface, and game mechanics were only slightly improved from the first game, and there were a lot of hunt-the-pixel subquests.
In summary, only the second game is really worth checking out, and expect it to be hard to get into and/or stick with.
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Also, a bit of trivia about Betrayal at Krondor (one of the best PC RPGs ever in my opinion): It was made by Dynamix (who had most of their games published by Sierra), who had the original idea of using a flight simulator engine (for which they had been mostly known for) as the graphics engine for an RPG. It looked ugly as hell, but the interface was one of the best ever, and the music was excellent. The plot, gameplay, world size, and game mechanics were all very impressive as well.
The floppy version of the game was released for free, but if you find a copy make sure to patch it because they didn't release the final version for some reason.
Also, they did make some sequels, of sorts: There was Betrayal at Antara (which I never played) which was marketed as a sequel, but really was a totally separate game that was only connected to B@K in that it used the same engine. The true sequel was Return to Krondor, which was one of Sierra's first 3D Windows games. It used pre-rendered 2D backgrounds (which I loathed the use of in 3D games due to the inevitable occurence of confusing and odd camera angles) combined with 3D characters and items. Some people praised it highly but I was never able to really get into it, despite thoroughly enjoying the books on which the series was based.