If you are choosing a technology stack based on "Whats Hot" rather then "What provides the best solution for my team and my problem" then it doesn't matter what you choose, as it will probably be wrong.

Is your team heavy with javascript developers? Do you have a need for an event-driven framework that can handle large load? Great, here comes node.

Is speed of development and a wealth of 3rd party libraries for almost any need critical to your ability to get started? Well, RoR has you covered.

Every language has strengths and weaknesses. Picking a tech stack is a decision that should be based on your needs.