I gave super Mario bros a 9.5 rating for the following reasons:

Graphics:
This game has great graphics for the time. I would have given it a high rating if the pixels weren't as view able. I know you can't really see them in the background but when you look at the goombas, koopas, etc. They look kinda square. I know if you say look at a koopa's shell it looks round but when you look at closer its kinda square. But hey that's just my opinion. Now lets look at the good things about the Graphics:
I like how the background doesn't show pixels I think that really good for something of basic plain blue (not counting clouds). I love snow levels I just think it looks cool with the way pipes are white. I also like how every level ends with Mario going to a castle.

Sound: Almost all of the Mario games have some tie to these songs and the reason why is because there GREAT!
There great because the music is happy out in the over-world, the music is (kinda) mysterious when underground.
And when underwater it feels like your swimming! I mean when I go swimming I sing this song cause it feels so much like swimming! (Also its a great song) The castle music feels like your in a place evil and full of lava. And of course that it is a place full of lava! Although I gave this a ten I would like to say is that I wish there where more songs. The four songs I have listed are the only songs in the game expect when you find the princess. That's a nice way to move into my next rating:

Story: The plot can be summed up in this line: damsel in distress. All it is Bowser kidnaps the princess and Mario sets out through the land to find him. I gave this an eight because this is the story that started it all. Not just in Mario but in a lot of games. I mean in Zelda Gannon kidnaps Zelda, and in sonic 06 Eggman kidnaps Elise, many other are out there but those are the only that are coming to my mind.
The story might be small but it started a huge line of plot for many games so I think it should get an eight.

Depth: This game has 32 level in all. You only need to do 10 to beat the game but to get the best experience I recommend do all 32. (I'm not done yet!) This game world  fell expansive due to fact that your moving through so many places. Whether it's going through a deep cave or a large plains, going across an ocean or walking through a evil castle this game has tons of places that make the world fell huge.

Addictiveness: This game has so great level design and the fact that this the first Super Mario game you will keep coming back for more.
And there are so many secrets you will almost definitely find some every time you play

Although I wish I could end this there, I still have to do one more category:

Difficulty: I gave this an eight this might just be because I suck at this game but to me after the first 3 or 4 worlds it gets quite hard. I have never beat this game without warp pipes or restore points on my 3ds. After world 3 a new enemy appears called lakitu I have always find this guys every challenging because they float in a cloud and drop enemies. And in world 5 bullet bills appear which are big bullets flying at you. Combined I think lakitus and bullet bills combined with tricky level design make this game quite difficult after the first few levels.

Thanks for reading!     
 

I never thought about Mario setting the tone for other games with save-the-princess. Interesting...

Anyway that was a very good review. Your structure is clear and you gave enough details so we know what the game is about. It did not occur to me to look at the enemies closer to see their pixelation... The turtles' heads are very square, for sure.