You could run Ubuntu Mate on your Pi2 and Pi3, which uses Ubuntu's ARM apt-get repository:
https://www.raspberrypi.org/downloads/
I did test this recent Ubuntu (Mate) 15.10 on the Pi3 and it worked fine, even with the Xubuntu desktop apt-get installed. Probably also Ubuntu Mate 14.04 LTS from an archive or so should work. But 15.10 is nicer, and 16.04 LTS is in beta mode now. :-)
However, Raspbian brings new software improvements from the Pi Foundation like their nice OpenGL alpha driver, WLAN and Bluetooth driver, and other things to come, which aren't there in Ubuntu for the Pi. And since Ubuntu and Raspbian are both Debian based, you can always apt-get Raspbian to "look and feel" very Ubuntu like.