Can I upgrade this?

I drank the "apple juice" last year and bought my wife an iPad for her. Then March of this year we bought the newest iMac which we lost when we got robbed in June. So to fill this void of an apple computer, we bought a used iMac G5 20-inch iSight off of Craigslist. It currently has OSX 10.4.11. We miss Facetime, especially since we both have iPhones and the iPad. Is it possible to upgrade this to the latest OSX? I was told that if we can upgrade to at least 10.6.6, we would be able to use Facetime. Also, would upgrading the OSX affect the programs that were already installed on the computer? I have adobe creative suite and would hate to lose it. Any help would be greatly appreciated!
Thanks,
Shane

Unfortunately, Leopard 10.5.8, is the latest OS compatible with non-intel Macs. Since a copy of Leopard will set you back $100 (easily) you are better off selling your G5 and trading up to an intel Mac.