Although English is the most-contributed language, one of the goals of Common Voice is to support languages that wouldn’t normally receive attention from commercial providers.
The most-contributed language is Catalan with 3678 hours recorded vs. 3395 hours in English https://commonvoice.mozilla.org/en/languages (The language list sorts your browser's UI languages ahead of all others, which is why English may appear on top for you.)
e.g.: https://commonvoice.mozilla.org/nl/listen