Is Polish The Hardest Language to Learn?

It's official. Polish is the most difficult language to learn. Mark Biernat of confirms my suspicions in his new article "The Hardest Language to Learn":
What is the hardest language to learn?
  1. Extremely HardThe hardest language to learn is: Polish – Seven Cases, Seven Genders and very difficult pronunciation. Average English speaker is fluent at about the age 12; the average Polish speaker is fluent in their language after age 16. 
The author compares Polish with other languages, commonly considered as impossible to learn and knocks down stereotypes. In my opinion it's really well written and contest-related. I highly recommend reading it!

If you're still not convinced, have a look at this. How do we say "two" in Polish?

How to say two in Polish
How to say two in Polish?
So, do you agree? Is Polish do hardest language to learn?