It's not very pretty and its story sucks, but holy cow, it plays like a dream!
Too bad the game isn't as pretty as, let's say, Secret of Mana. The environments are not very colorful and look pretty much alike. There's just not a lot of variation. The use of magic can be quite impressive though, too bad you practically don't use it.
However, Terranigma, despite these problems, still is an amazing action RPG. Battles are fought real-time, without being transported to a seperate fighting screen. When you explore a dungeon and you encounter an enemy, you just run up to it and hit it with your weapon. It's -that- simple. This ensures a brutal pace throughout the entire game. You can basically run through the entire game, there are not penalties for running and fighting (which is the case in Secret of Mana). The opposite is true as a matter of fact. You can perform some "special attacks" by combining running, jumping and attacking. Some attacks are more effective when used on specific enemies, but the difference is hardly noticeable.
Magic use is limited in the game. To use magic, you have to own rings which can be purchased. To buy those rings, you have to pay cash AND magirocks. Those magirocks can be found throughout the game, but they are limited. However, the biggest problem is the fact that you can only equip one item. To use magic, you have to equip the magic box. But you usually equip some healing potions. It's wildly annoying to navigate through a menu just to use some magic. Especially when it's not real effective anyway.
The big star in the game is the world you play in. Nowadays it's not that unique to have some influence on the world as you play through it. However, back in '95 or '96, it blew me away. Your actions, your decisions have a real influence on the game. When the king of France dies, elections are held. You can choose to vote for the conservative candidate or for the progressive one. When you visit the town later, it has grown (or it hasn't, depends on the choice). I absolutely loved it.
There are some minor technical issues however. Boss fights can be tricky. Or can be a complete breeze. I tried a boss fight when I was level 25 and I didn't stand a chance. My hits barely registered, but the boss was able to cut down my hit points with ease. When I leveled and reached level 26, I tried it again. I suddenly was able to beat the boss with ease. It's really weird, but I guess that's just Terranigma's way.
All in all, Terranigma does have it's quirks, but I honestly couldn't care less. The world you play in is big, with lots of things to explore, and you can actually change things in the world. The actual gameplay is terrific too and the game really benefits of its huge pace.