if u have 3-4 hours, then i would suggest you :
Jet d’Eau, the Rade ( visible from most of the Lac Léman waterfront ) and can see daily from 10AM to 11PM.
Cathédrale St-Pierre, Place St. Pierre (At the highest point in the Old Town). Please check the timings at nearest tourist office before going there.
get more geneva travel tips at :
http://geneva.travel/?page_id=148 about 6 years ago