@DiskDoctor
Red Hat Fedora alone has 12 million active users across Fedora 7, 8, 9 and 10 releases. Red Hat counts unique IPs connecting to their repositories, more info
here. Ubuntu claims a similar amount of users, more info
here. And there are other big/popular distro's like Debian, Mandriva and Suse which have millions of users.
Linux is Linux, you don't compare AmigaOS's popularity to one distro, everybody and his/her dog can make a distro. There are probably more Linux distro's than active Amiga users ;-)