So, one of my friends thought of a really good question, what is your favorite block. So in response I, being a stereotypical person, say diamond in response. My friend replies with "Why, diamond doesn't do anything."
I was about to say, you have never played this game, when I realize, he's right. It doesn't do anything! It can make stuff and look pretty, but it doesn't do ANYTHING! I was tricked, so I thought, well I'll play your game, and asked him well, whats your favorite block? He says, and I quote "Grass, or maybe dirt, It's hard to tell..." I almost screamed, but then I realize, this must be a trick. He then goes on to explain his theory.

Dirt is the ONLY material capable of growing crops on. (Besides soul sand, but screw soul sand.)
This is the definition of rare: Infrequently occurring; uncommon: a rare event; a plant that is rare in this region.
It is infrequent for a block to have the proprieties of supporting life, thus making dirt the rarest block, in theory.

Grass and Dirt also feed animals like sheep or pigs. So without dirt, we would starve to death and be helpless to change it.

Dirt also makes up the ground, in other words, mining would be boring if you knew where everything was, but dirt covers that up.

I hope this changes your opinion about what the best block in minecraft is, thank you for reading.