Final Fantasy Legend is cool because it is the beginning of the SaGa series and it has some unique aspects to it. It plays as a pretty boring, straightforward RPG though, so there isn't much to recommend it other than for its historical relevance.

Final Fantasy Legend explores character advancement in ways that are ambitious and unproven for the time and has three different types of characters (humans, mutants, and monsters) you can use to fill out your party however you want. This is interesting and I liked being able to focus on the types of characters I wanted, but it ultimately doesn't make too much of a difference. I don't like the monster mechanics in these games, so I only used humans and mutants.

Although advancement is unique, combat in FFL is pretty rote and can be tedious. Most enemies in the game can be burned through pretty mindlessly with your best attacks and spells.

The story in Final Fantasy Legend is pretty simple but satisfying. Your group is trying to climb a tower that travels through multiple worlds in order to reach a fabled paradise.
There are a lot of cute, short, character driven stories on each world as you traverse them, each of which varies wildly in theme and tone. It keeps things interesting and there are quite a few memorable characters you meet along the way.

Final Fantasy Legend is an interesting relic that is cool to look at in comparison to where Squaresoft went with the SaGa series after it, but there isn't much to make it worth playing through now.