They are roughly at the same level of google trend popularity if you use just language names (w/o 'programming'):

http://www.google.com/trends/explore#q=python,ruby&cmpt=q

EDIT: This one is maybe more accurate (w/ 'programming' as selected category) and it shows that interest is roughly the same on average: http://www.google.com/trends/explore#cat=0-5-31&q=python,+ru...