You can also install ncdu or filesplus, which has the funcionality to list folders by size. Or folderpie. Note that Ncdu is a terminal app.

I had more than 5 pages of icons of installed apps at my homescreen, no games though, and / partition was just below 2GB. So i decided to repartition as 2GB root, 2GB user and ~10GB MyDocs. Works for me, but don't follow me on this. I used gparted on linux, on ubiboot maintenance mode.