Darren at ProBlogger asks, what is great content? ...

I need to think about it.  For now, I'll say that great content ...

• Surprises you.  You learn something you didn't expect.
• Lifts you up.  You're inspired to act.
• Echoes in your mind. It sticks. A new idea is forever etched into the canvas of your mind.
• Makes you feel.  Maybe happy, maybe angry, maybe sad.  You don't feel indifferent.
• Changes your game.  You can't wait to test your new skills on the unwary.
• Leads you to an "ah ha".  It wrinkles your brain.  A shiver runs up your spine as you connect the dots.
• Answers a burning question.  You always wondered why.  And now you know.
• Solves a relevant, valuable problem.  Life tests us.  It's nice to have the answers.  

To put it another way, it's got character, emotional appeal, and logic you can't help but to tango with.   It changes what you think, feel, or do.

PS - I distinguish great content from great writing though they share some common attributes.