If you like a car enough to want to buy it – that's popular. If you want a car more than ever before, or if your reaction to a new car is overwhelmingly positive, that makes our hot list. Some of the vehicles on this list made it because of improvements made – the 2007 Hyundai Santa Fe comes to mind -- while others made it based on the rousing ovation they received from our users upon introduction. The list is based on two basic criteria: for existing or redesigned models, it's a significant increase in purchase request activity. For new cars, we look at its initial reception.