Perfection, from graphics, to gameplay, to music.
You play as Yoshi, the lovable green dinosaur thingy, who has come across a baby that literally fell from a sky after the stork that was carrying him was attacked by these mean propeller headed dudes who wanted to destroy baby mario and luigi before they came to destroy their master, Kamek, this weird wizard dude, later on in life. Throughout the game you are Yoshi with Baby Mario on your back on your way to this dudes kingdom to get baby luigi back from baby Bowser and Kamek in their castle.
You are thrown into a beautifully crafted cartoon world, where everything looks hand-drawn with crayon and color pencil by babies themselves. This sounds like a bad thing, but this effect is beautiful. Everyone level is gorgeously colorful and vibrant and even the background is nice and detailed, with every inanimate object having a happy smiling face. Considering this game is on the SNES, they did very well with very little and made an extremely beautiful world for you to adventure into.
The sound is just as flawless. It's made up of flutes and other wind and some percussion instruments to make child-like, tribal-ish music that fits the surroundings very well. Although the songs are looped, they never get boring, and always just add to the dazzling surroundings, even as they get darker and darker the closer you get to the end.
The gameplay is made up of puzzles, platform jumping, enemy avoiding, and plenty of creative boss-fights. The game is incredibly inventive with the gameplay as each level has a new unexpected twist. Sometimes you'll be fighting parana flower, and other times you'll be funning away from a giant black pack man that's trying to eat you. The games gets increasingly challenging, and although the levels may be all there is, they'll still keep you entertained.
Even after you beat the game, you can go through each world and get a perfect score on each one, which unlocks a bonus level in each world. This essentially doubles your playtime and gives you plenty more to do.
There's nothing you can say negatively about this masterpiece of a game. The only flaw you might find is it's difficulty, but that only makes it last longer. It is a challenging, inventive, and genius adventure and will leave you wanting to play it all over again.