Gerald Genta designed many legendary timepieces, including IWC's classic Jumbo Ingenieur from the 1970. He also was famous for designing Patek Philippe's Nautilus model and the Audemars Royal Oak --in fact, his designs are credited with the then-revolutionary idea of steel luxury sports watches.
There is some controversy regarding whether he also designed some of IWC's other models, including the Polo Club, the Golf Club and the Yacht Club II. You can read about that through an archives search.
But regardless, his influence on the watch industry in general and IWC in particular was significant. His passing is sad news.