What is the best-selling film series on VHS?

When VHS ruled home entertainment in the '80s and '90s, some movies became instant must-haves while others gathered dust on video store shelves. Individual blockbusters grabbed headlines for massive sales, but the real money was in getting families to buy direct-to-home sequels. Parents would purchase the original, then eagerly snatch up each sequel as soon as it hit stores, creating a franchise goldmine that completely bypassed theaters. Which film series became the VHS sales champion?