Just like Zelda 2 and Super Mario Bros 2, Final Fantasy 2 was a very different take on the series compared to its predecessor. I really enjoyed the game, unlike the 2s on the other two franchises I mentioned before, but FF2 took a strange road. They went for a training system, meaning that, you upgrade the level of something the more you use it. To improve your magic, use that magic. To improve your normal attack, keep using. But to improve your health/defense, you have to get hit and don't heal yourself till the end of the battle...what? Yes, thats true.
This gave the chance to people to abuse the system in later stages of the game, you could just fight level 1 enemies, hit yourself and keep finishing battles that way. But also was very bad in the early stages, making some of your characters never improve of that aspect because you had to keep them alive, therefore using heal. The later dungeon in the game was incredibly challenging as well, giving a bad taste toward the finish line.
But as positives go: The game has one of the best senses of what you're playing for, that I've ever seen in the RPG genre. The game makes you feel and see, how terrible war is and can be. They don't care about the player caring about a character and just killing it later. Everybody in the game is losing so much, a very nice and intense story telling, especially for it's time.