And no matter how superior Ubuntu becomes, Gentoo, Slackware, Red Hat, Fedora, and Debian are more important because they are the primal Linuxes. Everything else flows from them. They are the progenitors, and are essential.
Let's also remember non-Linux FOSS operating systems such as FreeBSD, NetBSD, and OpenBSD. From these also come herds of wonderful things such as routers, firewalls, drivers, network stacks, and stout high-demand servers. (Take a look at the top servers on Netcraft.)