Hi Kerstin,
That's definitely a fun question! It's really hard to pick a favorite planet because there are so many amazing things on our own planet and the other planets in the solar system. But if I were to pick a favorite planet besides Earth, I would say Saturn. Looking at Saturn through a small telescope is fun because you can see its rings. Saturn also has a magnetosphere and auroras, which I think is pretty interesting too. The Cassini mission to the planet Saturn has recently taken some images that I think are incredibly beautiful. I think they are great as both scientific data and abstract modern art! Most images of the planet Saturn show it as a sort of golden-tan color. My favorite images of Saturn show that the sky in Saturn's northern hemisphere can actually look sort of blue. This is due to the fact that Saturn's northern hemisphere is relatively cloud-free (compared to the southern hemisphere) and the atmosphere there preferentially scatters blue wavelengths of sunlight. You can see some pictures of the blue skies on Saturn here:
http://www.nasa.gov/mission_pages/cassini/multimedia/pia06142.html
http://www.nasa.gov/mission_pages/cassini/multimedia/pia06176.html
I can imagine that it would be quite awe-inspiring to be on a spaceship orbiting Saturn and to see the moon Mimas against the blue skies and the shadows cast by the rings as you swing around the planet and cross the rings from the southern hemisphere to the northern hemisphere!
Kris