The key difference to keep in mind with cars v guns is that there is no right to drive a car that is enshrined in our constitution. It is not a property right. YOu can own as many cars as you want, but until you meet the government rules regarding operating a car, you cant drive it.
All laws regarding cars concern their operation. The Constitution does not recognize a right to operate a car, just like the Constitution does not recognize a right to fly on a plane or a host of other regulated activities.
The Constitution does recognize the right to own guns. Which means the government does not have the power to take these away and any such regulation cannot be of the sort to limit one's ability to rightfully obtain their firearm, which is a right granted to them by an authority higher than government.
Now, I think the legitimate argument comes into play as to some of the terms in the 2nd amendment. 1) what does bearing arms mean? Is it limited to owning the gun or operating it? There are legitimate questions to be answered there.
2) It is recognized that government can impose regulations that are reasonable on guns. WHat would be reasonable. The 2nd amendment says nothing about ammo? is that included in the right to bear arms? This is a question to be debated as well. Just like cars, the government cannot take away your right to own a car (Right to life, liberty and property) but it can limit how you use that property.