The former NBC executive was appointed Monday to lead AT&T's Direct-to-Consumer business and chairman of WarnerMedia Entertainment, which includes HBO, TNT, TBS and truTV. He takes over for longtime HBO CEO Richard Plepler, who resigned Thursday.
In an interview with NBC News' Dylan Byers, Greenblatt blasted Netflix.
"Netflix doesn't have a brand. It's just a place you go to get anything — it's like Encyclopedia Britannica," Greenblatt said, according to Byers. "That's a great business model when you're trying to reach as many people on the planet as you can."
HBO has long positioned itself as the premium content option in an increasingly crowded streaming space. Netflix, Hulu and Amazon have all bolstered their on-demand video services with original programming in a challenge to HBO. And media giants like Disney and Comcast-owned NBCUniversal are about to launch their own services.
"It's getting to be a crowded field," Greenblatt told Byers. "We think there's room to carve out a very good consumer base for us."
Read more from Greenblatt on NBC News.
Disclosure: NBCUniversal is the parent company of NBC and CNBC.