In an interview in Dubai, where his Virgin Atlantic airline began flights from London this week, Branson said other companies offering space travel had not matched the progress made by the Virgin Galactic venture.
"A number of companies around the world are offering space travel but they haven't tested and built any space ships. They certainly haven't had test flights into space," Branson said on Wednesday.
"Virgin is the only company in the world that has actually achieved that," he added.
Virgin Galactic will offer space flights for $200,000, and says it has already received more than 150 firm reservations and taken $13.1 million in deposits.
About 45,000 people have expressed an interest in the trips.
The spacecraft to be used by Virgin is based on SpaceShipOne, which in 2004 won the $10 million Ansari X prize offered to the first private organisation to launch a reusable manned spacecraft into space twice within two weeks.
Virgin is building five models of SpaceShipTwo, a larger version.
"You'll go up under the mother ship, ... and then you'll have the rush of your life as the craft goes from zero miles an hour to 4,000 miles an hour, taking you into space ... enjoy weightlessness, see the curve of the earth and see the atmosphere"
The craft is attached to a larger plane - White Knight Two - for take-off from the ground, and then detaches at 50,000ft from the carrier aircraft before accelerating rapidly and entering sub-orbital space.
Virgin says customers will spend 15 minutes in space, including five minutes of weightlessness.
"You'll go up under the mother ship, attached to it; you'll be dropped away and then you'll have the rush of your life as the craft goes from zero miles an hour to 4000 miles an hour, taking you into space where you will be able to unfasten your seatbelt and enjoy weightlessness, see the curve of the earth and see the atmosphere," Branson said.
The entrepreneur says he plans to be on the first commercial Virgin Atlantic flight along with his children and parents - including his 91-year-old father.
Branson says safety is of paramount importance to the venture.
"We have to launch this on the basis that we're giving people a return ticket," he said.
"We have the best safety record in transportation of any group of companies in the world."
The venture has several competitors, including Space Adventures, a US-based company that has already sent three space tourists on a Russian Soyuz rocket to the International Space Station for $20 million each. The firm now plans to use Russian technology to send tourists on suborbital flights.
But Branson said competitors had not tested their spacecraft and he was confident Virgin was ahead.
He said he expected Virgin Galactic to be a commercially viable venture that eventually makes space travel accessible to millions of people.
The venture hopes to fly 50,000 people into space in its first 10 years of operation, and Branson said that with time space travel would become cheaper.
"I don't think that anything like this could survive unless it was commercially viable," he said.
"I think this can be a commercially successful venture as well as an awesome adventure."