Linux probably supports more platforms these days. But it often requires vendor-specific kernel forks, specific distributions, etc. NetBSD is impressive because

Linux probably supports more platforms these days. But it often requires vendor-specific kernel forks, specific distributions, etc. NetBSD is impressive because it can be (cross-)compiled for many systems using the stock distribution without much effort (build.sh script). Disclaimer: I haven't used or looked at NetBSD since 2006-2007 or so, but I think this is still accurate.