It's the best 2D Zelda that you can play, bar none. It has an exciting and colorful overworld with dungeons that can be a bit tricky and an amazing second half that can test you!
The story at the time was amazing, going back to it now it's your standard fair for storytelling, but it doesn't make it any less cool to see it play out. There are some interesting characters on your journey that give you side quests for either extra hearts or a neat item, and most of is not tedious to go through. The game is split into two separate worlds, the light world and the dark world, with the latter being quite difficult to get though if you're not prepared for it.
The bosses are also pretty entertaining as well, especially in the dark world. And the music is amazing for this, and a lot of the music that is still being used comes directly from this game!
If you love Zelda, and the top down variety, you'll need to play this one, it's a clear example on how it should be done!