What's your preferred language?

HTML is not a programming language so please don't consider it as such. HTML is a markup language (just like Markdown) that is used to create hyper-text websites.
As far as preferred language is concerned, in 2016 there is no such thing as only one preferred language. There is a learning curve that you have to follow.

Personally, I am a front-end web developer which means I am using the following languages to build the interface of web applications:
HTML (Markup Language)
CSS (Style-sheet Language)
JavaScript (Client-side Programming Language)
jQuery (JavaScript library)
AngularJS (Client/server-side JavaScript framework)
Ionic (JavaScript framework for apps)

There are also React.js and other frameworks and libraries, of course. But the aforementioned ones are the becoming or are the standard of front-end web development.

Of course, there are (primarily) back-end programming languages such as Python, C++, Ruby on Rails and more.