The car itself is definitely not green (as you note, very high consumption, moderate to poor tuning and condition of many of the engines, no or very limited emissions controls), but the fact that 95% of them are not used for daily transportation I would think renders this discussion moot.
On that flip side, they are very pleasing to the eye, and so enhance our environment. They keep many grown men confined to the garage and the keyboard, so we have less time to spend in other cars, on motorcycles, in boats or engaged in other environmentally taxing activities.
From an environmental perspective, live events should be discouraged. Take the 2005 Ohio tech session: the number of flying and driving miles (California, Dominican Republic, Netherlands to name a few) add up.
But if the 'peak oil' and similar predictions bear truth, within a few short decades, our cars could well be no more than stationary museum pieces. Now there's a scary thought ...
Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic