The phrase "top of the sales charts" means that a particular product or service is selling extremely well and has achieved high levels of success in terms of sales. Full definition
It has long set the pace by continually introducing new technologies, increasing towing and hauling capability, adding luxury features and carving out new segments — a playbook that has kept the F series on top of the sales charts for 41 years. (autoweek.com)
Thanks to its generous payload capacity and the strong engines, the vehicle was fairly practical and even since its debut, has managed to stay on top of the sales charts. (topspeed.com)
And the Civic's reputation for reliability should help it stay atthe top of the sales charts. (automobilemag.com)