Personal Opinion.
It's best because I feel human after watching it.
I cried. Not a lot of tears. Like 3.14ml of it.
My tears contains some minerals.
You have to understand, I hardly cries. I'm usually souless(or just laugh stupidly), to drop more than 2.718ml of tears is a huge success for my human emotions.

The part where I found deeply touching.
When WALL-E got crashed. [The trigger of my emotions, it's a gate of in control, when opened, I get flooded by emotions.]
When WALL-E lost it's memory.

How can a machine have human emotions?
Does intelligence automatically spawns when there is enough complexity?
Why did WALL-E love EVE?
Is it allowed for machines to love?
Does EVE have iPod functions?
Is this movie have a hidden level of code that reveals a major global conspiracy?

Ohh. too much to bear to feel human again. Sleep time.
Must go back to the machine level tomorrow.