The Final Fantasy series is arguably one of the most recognizable and well-known gaming franchises out there, and they've made some seriously awesome games (FF6 - if you haven't already, go play it.), but they've also made some games that weren't too well received.
Mystic Quest was pretty much intended to be a dumbed down and westerner-friendly RPG to try and widen the appeal to Role Playing Games, which, at the time, we're essentially a niche market.
The gameplay differs from that of other standard RPGs in the sense that the random battles are done away with and replaced with visible enemy sprites - which are stationary - and "Battlefields." The overworld map is still there, but instead of free exploration, you have a grid based (think Super Mario Bros. 3) map with set destinations. Some of these destinations are the aforementioned Battlefields which allow the player to level up the main character "Benjamin" and any, if applicable, of his compatriots. They are essentially a string of battles purely there to grind for experience.
Also, character customization is gone, armor and weapons acquired are essentially permanent, with only the ability to switch which weapon you use in-battle and the various locales on the map.
Clearly, it was a pretty simplified version of a traditional RPG, and for the most part, it was well received, garnering a 7.25/10 from EGM and a 3.725/5 in Nintendo Power, but the mission of bringing the RPG genre to the mainstream wasn't accomplished with the release of Mystic Quest as was hoped, because this feat was of course later accomplished with Final Fantasy 7.
Onto the meat and bones. Mystic Quest's graphics aren't anything to really write home about, and the plot is dead simple - find a handful of crystals that control the elements in order to save the planet, kill this "Dark King" fella' and go home and sleep.
While those are some of the negative points of the game, the music is pretty damn good. It's composed by Ryuji Sasai, who also composed games like Tobal No.1, Bushido Blade 2, and others. While he may not be a big time composer like the obvious Mr. Uematsu, the composing work is very good, with a nice metal influence in pace and in sound. (Listen to the Boss Theme, and the Dark Castle theme, they're amazing.)
Let's also get another thing straight before we continue - I'm a hardcore FF player, although I detest most of the recent ones with a few exceptions, and despite my expectations from an RPG, and the difficulty therein, I was strangely pleased and satisfied with my play through of Mystic Quest. The game is extremely easy, and I mean, pants-on-head-stupid easy, but it was still a lot of fun. Beating the hell out of enemies in the battlefields was repetitive, but rewarding, pummeling bosses while thoroughly enjoying the music, and eventually decimating the Dark King with "Life" because he's undead, therefore I dealt damage to him over the in-game damage cap.
A lot of my friends and acquaintances almost entirely disregard two games in particular from even being considered a Final Fantasy game, and that's Mystic Quest and Final Fantasy 12. I always ask why they don't like Mystic Quest, and I get a lot of the above - it's too easy, too simplistic, not a real RPG, and while they're technically correct, it doesn't necessarily make it a bad game. I think that while it's easy and simple, it's still worth a play through, and the music alone makes it worthwhile, as well as the simple and enjoyable game play.