Netflix (NASDAQ:NFLX) has become the unchallenged best-in-class standard bearer for streaming services. You could argue that its closest competitor, HBO, which had a roughly 25-year head start, is a very distant second and that nobody else even comes close.

The streaming leader has moved from delivering DVDs of other company's movies to streaming content from other providers to being a global leader in delivering original programming. Netflix closed the first quarter with 148.6 million paying customers globally, with 60.23 million of them in the United States.

To put those numbers into context, the entire pay cable market in the U.S. is about 93 million homes. Netflix has newly two-thirds as many paying customers just in its home market and about 55 million more globally, but the company's CEO still sees a huge market where it can gain share.

The Netflix home screen.

Netflix has become the clear leader in its category. Image source: Netflix.

Is this Netflix's next mountain to climb?

The streaming giant expects its U.S. growth to slow. In fact, after adding about 1.75 million subscribers in the U.S. in Q1, it forecasts closing Q2 with only 300,000 more. Some of that may be the anticipation of increased churn due to its recent price increase.

Global growth will be better, with another 4.5 million or so paid subscribers expected, but that's not where the biggest opportunity exists. Chief Product Officer Greg Peters explained during the company's Q1 earnings call that the company is not the leading entertainment choice -- or even one of the bigger ones -- when it comes to people using their phones.

"I think the most important headline message there is ... how much time we don't win on the mobile experience," he said. About "97.5% [of the time] around the world, people are using other different entertainment services, other ways to enjoy their time on their mobile phone."

Peters believes that mobile can be a way for the company to add subscribers. He wants the company to leverage its existing relationships to make that happen.

"It's a great place for folks to find out about Netflix, to sign up for the service, even if they're signing up for the service on mobile and then they're watching on other devices like the TV, which we see as a common paradigm," he said. "It works really well with our partners, because whether it's handset partners, which we can work to sort of preload our application on, or actually the mobile operators, which we can work on increasingly doing things like bundling Netflix as part of their standard offering, which you see us doing more and more around the world."

What's next for Netflix?

Clearly, Netflix can make more deals like its partnership with T-Mobile. There the wireless carrier actually pays for many of its customers to get the streaming service. Globally, it seems very likely that other carriers would want to bundle the streaming service with their mobile plans or use it as a carrot to get customers to sign up.

What Peters did not mention is that the eventual launch of 5G service in the U.S. and in other parts of the world should open the company up to new subscribers. Watching streaming video on a smartphone that's not Wi-Fi-connected can currently be a frustrating experience.

That broadband limitation may keep some customers (those who primarily use their phone as an entertainment device) from joining. But as that barrier goes away -- and 5G even allows some of those customers to stop paying for home internet -- Netflix should have a large new pool of potential customers.