I agree, looking at some of the old classic zeds, even now, they are not worth much at all, so i dread to think exactly how many decades you`d have to wait for a 350z to start holding their value or even going up in price.
Who knows what future generations will regard as Classic, in any case I've never subscribed to the theory that only good cars will become valuable over a long period of time....it's all down to how rare the car has become, take for example the Jowett Javelin, a car that was besieged with problems yet even a wreck fetches good money these days, or the Ford Anglia that had one of the highest production runs of any U.K car. One of these in decent nick will set you back a small fortune. Two of the worst cars I've ever driven, The Morris Minor and The VW Beetle are now regarded as Classics . But, yeah, if you are waiting for The 350Z to become a valuable Classic then you'll have anything from a 25 year upward wait.
Pete