"Westworld" series surpassed "Game of Thrones" pilot episode by more than a million, making it HBO's most-watched premiere with 3.3 million viewers.

BBC reported that according to Variety, the figures are based on those watching live in television and people watching on HBO's streaming platforms.

Westworld beat the 2014 crime drama series, True Detective, which attracted 2.3 million viewers across all platforms.

Additionally, it also outshine the 2011 popular series, Game of Thrones, which attracted 2.2 million television viewers on the evening it premiered.

The casts of "Westworld" series include Evan Rachel Wood, Jeffrey Wright, Thandie Newton, Luke Hemsworth, Anthony Hopkins and Borgen's Sidse Babett Knudsen.

Meanwhile, the debut episode of "Westworld" has mixed reviews from critics.

"It's a good start for the show, even if it feels at times as though you're being thrown in at the deep end. Still, the cast is several feet deep with impressive performers already and the world itself is a thing of designed beauty." - Empire's James White

White added, "There are worrying elements - it's quick on the trigger finger when it comes to narrative tropes such as violence against women and casual nudity, but it remains to be seen how the show tackles those themes going forward"

"Yes, there are a lot of breasts and, so far, the women are either robots at the mercy of punters or professionals not listened to by their colleagues," - The Guardian's Julia Raeside.

"But otherwise, this is an impressive opening that ponders the qualities that make us human without bludgeoning us over the head with the differences between man and machine. And the cast is terrific," she added.

The series was brought to screen by Jonathan Nolan and Lisa Joy.

"The news will no doubt reassure HBO programming president Casey Bloys who was undoubtedly facing pressure to source a new hit following the news that the channel's most successful TV show, Game of Thrones, is gearing up to an end; it's final season will air in 2018," Independent.co.uk wrote.

"While Westworld may still have a long way to go before matching that show's success, things are looking good for the sci-fi western which reportedly has five seasons mapped out."