The Sierra series that you guys are talking about was actually called "Quest For Glory" not "The Hero's Quest." The first one was originally going to be called that, but there was already a game out by that name, so they decided that would be too confusing. Anyway, as I said, the series as a whole is called "Quest For Glory" and although they're hard to get your hands on these days (I played them excessively as a kid, and luckily still have my collection) if you can find a copy, I'd highly reccommend it. It's one of the best series I have ever played. Very humorous, a lot of fun, and extremely colorful. The first game was called "So you want to be a hero?" and was set in a medeival/germanic valley. The second was called "Trial by fire" (the one you played) and was set in the desert. It's the only one of the series that had a text interface and was never changed, although
AGD Interactive is in the process of revamping the system and graphics, which looks to be very promising. The third was called "Wages Of War" and was set in an Egyptian land. The fourth (and my personal favorite) was called "Shadows Of Darkness" and was set in the Transylvanian like land of Mordavia. Shadows of Darkness remains one of the most fun games I have ever played. The last game in the series (Dragon Fire) is not always accepted by fans of the first four games, but I thought it was enjoyable nonetheless. Gave you more options than the previous ones did. The games offer you the three traditional character classes: fighter, thief, and wizard, with the option to become a paladin if you were a fighter. Anyway, enough of my long-windedness, but basically, if you ever have the chance to get your hands on a copy of these games, go for it. Some of the most interesting characters and funny situations only matched by the isle of wonder in King's Quest 6, for those of you who know what I'm talking about.
As for Gabriel Knight, I played through the series only last year, and absolutely loved it. It's not really an RPG, per se, as the characters have personalities, and won't just do whatever you instruct them to. The graphics aren't state of the art, but in my opinion, the mysteries are interesting, the story and characters are compelling, and they have a lot of good wit and humor. Slightly mature themes, but nothing explicit. The first one is called "Sins of the fathers" and is a story of voodoo set in New Orleans. Great game, great atmosphere. Old graphics, but you'll barely notice them. Good game, with that great New Orleans atmosphere that's always present in creepy bayou/voodoo movies/stories. A lot of fun. The next, as someone said, is called "The Beast Within" and is done with film. One of the few games that I actually thought this worked for. It's, obviously, about werewolves, and in my opinion, had one of the most complex and compelling "antagonists" I've ever seen in a game. And I put that in quotes, because, truly, said antagonist was hard to hate. These games truly aren't afraid to deal with anything, either. There were strong homosexual overtones in that game that were kind of surprising for that time, and were handled in a very tasteful and classy way that you would be hard pressed to find even in today's culture, which deals with these things very openly. The third, in my opinion, was the weakest point of the series. It was called "Blood of the sacred, blood of the damned" and dealt with vampires and with the subject matter dealt with in The Da Vinci Code. (Down to the holy grail and knights templar and priory of scion and everything. Apparently both the game and book were inspired by the same source.) It was an interesting mystery, but for me the puzzles were a bit more "out there" and the villains felt extremely cheesy and unengaging compared to the well-developed villains of the previous two games.
Please forgive my ramblings. =/