Re: "This depressing picture"? Aye right...
Well, the more market share you have, the more malware you attract - just because [insert little-known-OS name X here] hasn't had malware/security problems does NOT equate to being more secure, in fact very much the opposite is the case.
Much like encryption, the better known / more attacked a target is, the more hardened it becomes over time. Security by obscurity is well documented as a shaky prospect... even Microsoft (who I'm no fan of) are starting to open source core parts of their systems [see .NET framework] which is a huge move in the right direction.
FYI, I think that most people that get malware on Windows machines these days are people who a) run as administrator and b) click on links from Nigerian princes and c) are dumb enough to use a web browser which is closely tied into the operating system (facepalm Microsoft, please give that one up - there's nothing for you to gain by offering your own browser anymore! Do us a favour and uninstall the damn thing as standard!).