Christopher Becke, a high school physics teacher, made this outstanding size comparison showing what the Comet 67P/Churyumov-Gerasimenko would look like next to famous spacecrafts from science fiction. His images show the comet next to ships from Star Trek, Star Wars, Firefly and Battlestar Galactica.
And the comet is so small! Or I guess, maybe our imagined sci-fi space ships are too big? Either way, it's still so very impressive that the ESA was able to land a robot on that rock.
Additionally, the ESA compared the size of the comet to various European cities too: