Elon Musk has SpaceX. Richard Branson has Virgin Galactic. And Jeff Bezos has Blue Origin.

These titans of entrepreneurship are ushering in a new generation of human spaceflight.

So who's the most important space entrepreneur? "There are different levels of importance," Terry Virts — a NASA astronaut who has spent seven months living in space, commanded the International Space Station and completed three spacewalks — tells CNBC Make It via Skype video conversation in Dec.

As far as getting the public excited about space, "Elon has done a great job with that," Virts says. "[Musk] has lots of big visions."

Photo courtesy Terry Virts

Branson's enthusiasm for space tourism is similarly important, says Virts. "Richard Branson is just fun. … He's a cool guy. That's a cool thing, that is going to inspire people," Virts says.

But when it comes to Bezos, the founder of Amazon and currently the richest person alive, Virts says, "Jeff Bezos is the real deal. His company is legit."

In fact, says Virts, the BE-4 engine Blue Origin is building, "I think is going to be the most important rocket engine of the 21st century. Lots rockets are going to be using it — government rockets, rockets launching telecom satellites and also people," Virts tells CNBC Make It.

"In the long run he's going to really make an an impact on getting to the moon, getting people in space and really impacting the 21st century space economy," says Virts.

Together, the gaggle of elite space entrepreneurs' companies are building the next generation of human spaceflight.