I would like to mention LFE. Lisp Flavored Erlang (
http://lfe.io/) is a great addition to the Erlang/Elixir world/ecosystem. Go on, test it out!
I work as an Erlang dev. It is really awesome. It has a simple and consistent syntax (even if don't like the comma, semicolon and period terminators), the most powerful native concurrency semantics I know, the best error detection and handling semantics, pattern matching (you make the compiler work for you), an awesome virtual machine that took correct design choices (gc per process, iolists for concatenating strings), incredible tracing support, good support for connecting with other programming languages, a good optional type system (Dialyzer, http://learnyousomeerlang.com/dialyzer) for detecting type errors and good patterns as supervisor, gen_server and gen_event . It also has a vibrant community that has created good libraries like Proper (QuickCheck-inspired property-based testing tool for Erlang) and Cowboy (simple http server).
I have worked with C, C++, Java, Ruby, Python and Javascript/NodeJs. I really like Python and Ruby as general programming language and for creating prototypes, but I would definitely use Erlang for any real backend project.