Python today has the best numeric computing libraries (numpy and sisters) which make it the most widely adopted language for scientific computing, ML, etc.
Ruby had Rails - the web framework that trail-blazed convention over configuration and rapid productivity and was considered leading just a few years ago. Ruby's popularity has waned since then as performance and scalability has become far more critical than plain productivity alone.
Perl had the best regex features and reporting facilities fifteen+ years ago. It has lost its crown and is rapidly declining since Perl 6 took forever and is basically a completely different language.