Being loved (I don't mean the physical love), appreciated and respected... sorry, I'm so bad, those are three best things :)

For me, it's waking up in the morning with the sun shining in my window.

Wow what a hard and general question.  I guess right now, I'd probably say living life is the best thing in the world. 

as for me, the best thing in a world is feeling balance with the world around me.

The most important thing for me is being happy.