Alexa ranking would be really important but it's also easy to hack. For example, i think you all know proxy websites. There are thousands of proxies around the world and you can login from each one to your website. Like that, you will hack alexa rank generating new visitors.
There are many websites in top 10,000 that don't have anything to do there. Alexa is not important,
PR isn't either, the most important thing is how much you're earning each day from your websites and quality backlinks that you have.