Web Application resources required Ruby vs Java

David Heinemeier Hansson says,

"Once you've tried developing a substantial application in Java or PHP or C# or whatever, the difference in Rails will be readily apparent. You gotta feel the hurt before you can appreciate the cure."

Who is David Heinemeier Hansson? David is...
What else he said about Ruby on Rails? Interview with David...
How popular he is? Well he ranked ...

Ruby on Rails - The 10 Most Marketable Web Development Skills

After the brief talk on Ruby on Rails at Twincling society which was successful and satisfactory, I am keen on writing and talking more on Ruby on Rails development.
So one of the FAQ's I face most is
What is Ruby on Rails and what is the market for it?
I stumbled across one such article "The 10 Most Marketable Web Development Skills", where the list of web development skills provided.

Note:

• This is not any comparison but just listing out current web developement skills that have market.

• The order of the list is not based on any popularity.