Most makes of cars once they start to become rare. may not be true classics but have a following in clubs and forums as we are seeing this now with the Gen 1 CTS. Over here you may see one or two a year, bar club events of course, then at most American car meets they are far a few between.
Even bad cars that had a poor reputation when they where new , once rare start to go up in value. Over here we had a not bad looking but some what iffy car called the Rover 800 coupe, Rovers attempt at taking on BMW and Mercedes, from the 1990's it did not go well. A few years backs you could not give it away, but now considered a classic by some and indeed going up in value . The CTS started life out as a great car, the first of a new bread of Cadillac , so maybe