That's a fun question! The logical place to turn for this sort of information are shareware archive sites, and two of my favorites are Versiontracker.com and Download.com.

Before we check those sites, however, it turns out that I also get a weekly Download Dispatch newsletter from CNet and it includes a top-ten Mac downloads list:

That's a staggering number of downloads, and when you consider that both versions of LimeWire do the same thing, let you access the bittorrent / peer to peer (p2p) networks, it's rather disturbing to realize just how many people in the Mac space are downloading tools that gain them access to [almost always] illegal copies of music, video, software, ebooks, and related digital content off these networks.

So are PC users any better? Here's what Download.com reports:

Ugh, a lot worse. With only a few exceptions (ICQ, IrfanView) these programs all about interacting with these p2p networks (LimeWire, Morpheus and Bittorrent) or avoiding virus and spyware trouble from unknown PC software. Speaks of the reality of life in the world of Windows, doesn't it?

Let's look at VersionTracker's Top Downloads for the Mac:

Phew, that makes me feel better. Probably partially because Versiontracker has a solid focus on utilities and related, there's a lot less dubious software on the list, and indeed there are some great applications on that list in my experience!

One more: Top Windows Downloads from Versiontracker:

So there you have it, across these various download sites. Do Windows people download more games? I don't think so. Do both Mac and PC users have a strong predilection for downloading stuff from peer to peer networks, perhaps not all illegal digital content, but ...

Hope that helps answer your query!