[andrewnez]

You can sort by stars, there's just not a UI yet: http://libraries.io/search?order=desc&sort=stars

Pypi is lacking in information but I'm working on pulling it from other sources to improve the quality for Python libraries.

[stared]

For PyPI it is rather straightforward to get downloads information: http://stackoverflow.com/questions/21419009/json-api-for-pyp... (along with some other data, e.g. categorization). See example: https://pypi.python.org/pypi/seaborn/json