Erika and Nacer's place is a fantastic option for staying in Geneva, and even more so if you are going to CERN. The apartment is right on the 14 Tram line and is about 15 min from CERN or 20 from downtown Geneva.
The apartment is great with light from all directions and wonderful views of the Alps. A nature preserve nearby is a nice walk. The room is perfect and has I had my own bathroom right outside. The best of course are Erika and Nacer, who were very welcoming and fantastic hosts. I am hoping I can stay with them again next time I go to Geneva.