It was Ford, they lost the competition to GM in the 70's , GM lost to Toyota, and Toyota lost to VW.
Since GM was on top, the number one biggest car company has changed twice in 2 years.
I just read Jamie Kitman's article in Automobile Magazine (great magazine, also read Ezra Dyer's article, the both of them are great!) and he points out that VW is on the verge of screwing up. They are making bigger cars, and making them cheaper, so they will be cheaper to buy and result in increased sales volume.
It's backfiring with VW. The Passat is only selling 10% of it's all time high in 2002. Not good.
Jamie looked the Passat over, and it's built in Tennessee for the American market, but it's not as nice as the German built Passat the rest of the world buys.
Jamie reports that VW has about a 1/4 million US customers, and wants to triple that and sell about 800,000 cars a year by 2018, but he tells us that the quality of the interior of the VW's is lousy, and thinks they are about to lose their market share to their competition. Time will tell.
The diesel version of one VW gets 52 mpg. Nice, but if a 45 mpg Hyundai has a nicer interior, I know I'd go for the better interior, and not worry about 7 less mpg while driving in a comfy and good looking surroundings.
FYI, the company that makes the most cars is Mattel.