I started out with Gentoo, maybe 10 years ago. It was the coolest thing, but later realized that I was spending a lot of time compiling everything and wanted these magical things called "binaries" instead.
So I switched to Ubuntu - Warty Warthog! I loved it because it was a minimal distro that was very useful and fit on a single CD. (I neither had lots of internet nor CDs available to me at the time.) Also, I never knew which options to select for a Fedora Anaconda install. So many packages - what do I want??
Then I tried Mint. It was neat, I guess, but never seemed appreciably easier than Ubuntu. I was hoping for an easier experience doing things like playing MP3s and displaying patent-protected GIF files, but I dunno, I never really got into it.
I did, however, get into the Cinnamon window manager!
Today I begrudgingly installed Ubuntu 12.04. It's more or less the only distro that anybody supports - you can get directions to install $foo (driver, software, Steam, what have you) on Ubuntu but other distros are hit or miss. And Ubuntu is more or less as updated as I care to be, a guarantee that I don't know I can get with other distros.
Mind you, I don't really like ubuntu nowadays. I'm not into Unity, I'm not into paid-results-in-system-search, and as a power-user, I was really unhappy when the switched from init scripts to upstart. But the community has widely adopted it as a 'standard' platform for their software, so, well, here I am.