The Toyota Corolla is the best-selling car due to its reputation for reliability and affordability. It has a low cost of ownership and excellent gas mileage, making it an economical choice for many consumers. The Corolla also comes in various styles, including sedans, hatchbacks, and wagons, making it a versatile option for different needs. Additionally, Toyota has a strong industry reputation for producing high-quality vehicles, which adds to the Corolla's appeal.