GM's bestselling luxury brand isn't Cadillac anymore.

General Motors has a healthy share of luxury brands on the menu, and Cadillac has been the bestselling of the lot – until this year.

According to figures released by GM and through a report by Automotive News, GMC has outsold Cadillac in the first nine months of the year, much credit goes to the Denali and AT4 trims that are available almost across the lineup.

Gallery: 2021 GMC Yukon Denali: First Drive

Of note, Denali and AT4 trims account for 40 percent of GMC's sales numbers, and on its way to represent half of the marque's volume this year, according to Duncan Aldred, vice president of global Buick and GMC.

The Denali and AT4 trims, which constitute almost all of GMC's lineup sans the Terrain, has put GMC to its highest retail market share in the first half of 2020 since 15 years ago.

This is despite the fact that the Denali and AT4 average transaction price is 30 percent higher than the industry. Aldred said that customers pay an average of $57,218 for a Denali and $53,989 for an AT4, which are higher than European luxury brands such as BMW, Audi, and Jaguar.

The Denali's and AT4's sales success went against the trend, with the U.S. market experiencing an overall decline in sales during the first nine months of 2020 due to the pandemic. GMC experienced a 16 percent drop due to inventory shortages and reduced fleet orders.

However, Sierra trucks saw a 6.8 percent increase. In contrast, there's an 8.8 percent decline for the rest of full-size pickups sold in the market. Chevy also experienced a 17 percent sales decline, while Buick and Cadillac were in for a 25 percent sales drop.