The equivalent for Gentoo is the overlay system. gpo.zugaina.org (which is the best total package index) claims to list over 100000 ebuilds for 56000 different packages (some packages have multiple versions in-tree), and I know their database is not complete, since I contribute occasionally to an overlay that they don’t index. Oh, and that also doesn’t include things like perl library packages autogenerated by g-cpan.

So, um, yeah, useful but not unique.