At the top of the best seller list, leading the chart of the favorite 50, rolling up the points and zapping the competition for the second week in a row, it's FROGGER!

But a new challenger is coming on strong. It's GALAXIAN, soaring to 14th place after just two weeks on the list. And watch out for DEFENDER, which is showing a lot of early strength.

If the names on this best seller list are unfamiliar, it's because they aren't books or records. They are home video games, and a California distributor has begun compiling a weekly list of the hottest items, based on its own sales to more than 3,000 retail outlets.

The "hot list," prepared by Softsel Computer Products Inc. of Inglewood, Calif., is distributed to retail dealers in personal-computer software and to the trade press. It is apparently the first systematic attempt to keep track of consumer preference in the volatile video games market.

Each weekly report lists the top 50 recreation or games cartridges, the 35 leading business programs such as VisiCalc and File Manager, and the bestselling educational programs, books and accessories among the 2,500 items distributed by Softsel.

According to the latest list, published on Monday, the 3,000 retailers nationwide who buy software and programs from Softsel ordered more Froggers than any other video game. Frogger, heavily advertised in television spots featuring a humanoid frog who takes cocktail canapes from a tray with its tongue, is a game in which a froglike character tries to cross a heavily traveled, dangerous highway. It was developed as an arcade game by the Atari division of Warner Communications.

Second on the games list is Choplifter, which involves a helicopter rescue of people on the ground in the face of artillery and air defenses, suggesting the failed U.S. attempt to free the American hostages in Iran.

Third and fourth places are held by two old Atari favorites from the arcades, Centipede and Pac-Man. Most of the top 50 are games on science-fiction and military themes. None is a sports game.

David Wagman, cofounder and chairman of Softsel, said the list grew out of requests from the trade press for information about "what was selling and what was not." Softsel kept monthly reports about what was moving out of its inventory anyway, and refined its records to prepare a weekly list, he said.

Each game, business program or educational program on this list is ranked according to its total sales, even if it is made by a different manufacturer for different equipment, he said. Frogger, for example, is licensed to one manufacturer for play on Apple computers and to another for play on Atari machines, but the two are run together on the total sales list.

Softsel, founded less than three years ago, claims to be the world's largest distributor of educational, recreational and business-related software for personal computers, with sales of more than $7 million a month.