Annemasse or Annecy
Although it is possible to get into Geneva in a light aircraft, they routinely close it to VFR traffic at busy times, and even when you are allowed in you will get messed about without local knowledge. If you still want to visit Geneva, fly to Annemasse instead. It is a very friendly GA airfield, nice restaurant at the club house, and although it is in France, Annemasse is basically a commuter suburb of Geneva, complete with convenient public transport links.
If you aren't going to Geneva, Annecy is very pretty, a few miles further south.
Finally, I always found the fuel (and all the other costs) in Switzerland to be rather more expensive than France...