As another commenter said, there are few reliable signals that one could really use for this in general, let alone to get a current ranking. Citations are a fine metric but typically it will take a few years for those to really build up on a paper. I would be very interested to see them expand these rankings beyond theoretical CS and into the other disciplines... particularly robotics, where US News doesn't offer a ranking.
Not really that hard. It's difficult to pass outright bad work through a top-tier conference, but above a quality threshold, it's basically a crapshoot; the reviewing process doesn't reliably separate middling from great papers. The very low acceptance rates (~10-15%) and very high inter-reviewer variance [1] combine to make it pretty random whether a given paper, of sufficiently "ok" quality, gets accepted or not. So the main successful strategy to accumulate a lot of papers in top-tier conferences is simply to submit a lot of decent papers to top-tier conferences. How many such papers a given professor can churn out depends largely on how many students, post-docs, and research scientists they can hire, which depends on funding.
[1] NIPS, one of the top-tier machine learning conferences, did a very interesting experimental study of this. http://blog.mrtz.org/2014/12/15/the-nips-experiment.html