I don't really think there's any particular language out there that makes you 'better', although I would suggest learning a variety of different types of languages (i.e. functional vs. imperative, static vs. dynamic, etc.)
Well, maybe not the basic syntax elements of a language, but there are idioms and techniques, some of which are quite language specific (or, are native or naturally expressed in some languages) and learning them will actually make you better.
