EarthBound 0, in my opinion, is one of the best NES games of all time. I think it goes beyond Super Mario Brothers and The Legend of Zelda, but that's just because of my fanboyism.
Anyways, most of the game you have control of a Preteen boy named Ninten, who's default name isn't shown in game, and other Preteens like Ana and Lloyd. ( or Loid) Also, Teddy optionally. (All who also don't get their default names shown)
Now, Down to Business.
GRAPHICS: 6.9
I honestly would've rated the graphics lower on any NES game, but I think this goes beyond little sprites on the overworld. You see the enemy's true look in a battle, which look VERY good for the NES. I'd say the overworld graphics are really pixelated, but hey, that makes the game look classic, and who doesn't like the classics? :3
I'd say the battle system looks pretty decent, but the bad fact is that it's all in black and white, which make it pretty bland.
SOUND: 9.9
I'd say I can headbang or listen in harmony to any of this game's music.
Although this game lacks game tracks, the ones it DOES have make up for it.
Pollyana, Bein Friends, and other overworld tracks soothe my soul. Queen Mary's castle, otherwise known as Wisdom of the World, can make me calm just about anyday.
But what I consider the game's main theme, The 8 melodies, are VERY soothing. They really help me after a creepypasta, trust me.
Now, onto the battle music.
Battle against a Flippant Foe, in my opinion, is a pretty bland song. Makes me wanna get those poor enemies who have that theme dead quick.
Now, Battle against a Dangerous Foe, which was good enough to have a remix in EarthBound, REALLY makes me start headbanging. I could listen to it for hours!
But don't even get me started with the Hippie Battle Theme. That song just makes me wanna get up and start dancing, I just love the sound of it!
ADDICTIVENESS: 10
Ohhhh my woord, I could play this game for hours. With this game's wonderful music, awesome story, and many more features, once I get on this game, (or any Mother game, actually) it's pretty hard to get me off. And after that I don't even trust my lamp because I'm a Mother fan, I'm weird like that, and I'm proud of it.
Story: 9.5
I'd say this game had a pretty good story.
In the early 1900's, possibly around 1908 or 1909, something strange happens. When people investigate, they send info back to the newspaper writer, George. The very day he publishes the paper, he and his wife, Maria, are kidnapped by aliens.
The aliens give them a baby to raise. That baby was named Geigue, Giyiyg, Giygas, or whatever the heck you wanna call him. While Maria did motherly things like sing him lullabies, while George studied the aliens. A few years later, ( 2 years to be exact), he runs off with the secret of PSI and leaves Geigue and Maria behind. What a great father.
When he gets home, he studies the ways of PSI, and guess what? He learns some.
When Geigue grows up, he is tasked by his alien race to not let the power of PSI spread to earth. But at the time, he doesn't want to hurt George or Maria's decendents, but he has too.
When he attacks Earth, he sends a poltergeist over to Ninten's house to ambush him and his family, but Ninten prevails. He learns he can use PSI himself, and must go on a journey to collect all 8 melodies and defeat Giegue.
Depth: 9.9
I'd say this game had a lot to offer. With a variety with enemies, good music,  good characters,and a good challenge, what else could anyone ask for?
Difficulty: 7.6
This game is actually pretty hard.
You have to level grind a lot. Mostly when you get someone new. This game's bosses are lethal; Starman Jr. and the Dragon are some of this game's very hard bosses. Some enemies pose a threat aswell. Oh yea, it's hard to gain levels, too.
OVERALL: 9.1
With all of this game's enemies, some challenge, good music, and a good story, what else could you ask for? 
This is a VERY good game for all you RPG - hungry people out there, and I really think you should try this.