FF2 has stats similar to The Elder Scrolls: Morrowind, you level spells up by using them, and level your ability to use spells and weapons by using them. There are no hard level ups, you just level stats, and they are constantly leveling.
You have to decide at the start of the game who is your tank and move him to position 1. You have to decide who your attacker is, and you can make him as a magic user and give your tank the best weapons, or you can have him be a generic sword fighter, and you have to pick someone to be the white mage. You can make choices here, but some characters grow some stats better and faster than others.
Stuff like that. In terms of pure gameplay, it's my favorite in the series, though I won't call it perfect. Shit like people blocking doorways and having to reenter rooms 6 times and getting random encounters because of it is super annoying, but that's what all famicom RPGs force you to suffer through.
you can also credit its writing team for deciding the future of all Final Fantasy games. The whole pretty boy hero with a pretty boy rival who rides chocobos, has a dragon knight lancer he hangs out with, and a white mage girl he's trying to fuck comes from this game. Most of the spells still in the series come from this game. Ultima is a major plot point, for example. The game has one of the most interesting world maps in any RPG.