Midfielder Franz Beckenbauer says, "If I was not playing for the Cosmos, I would still be in Germany."

The former West German World Cup star, who is still one of the game's best players, is not putting down the other teams in the 11-year-old North American Soccer League. He is only echoing the thoughts of world-famous teammates who have left their respective countries to form the finest team in the NASL.

"When my contract is up, I don't know what I'll do," said the 33-year-old Beckenbauer. "I don't think I'll play for anyone else. The Cosmos is the best organization, the best team."

There is no doubt about it. The Cosmos, who play the Diplomats Sunday at 2:30 at RFK Stadium, tower over the other 23 teams in the league. Since coming into the league in 1971, the Cosmos have won three NASL titles. They won the Soccer Bowl in 1977 and 1978.

Last year, the team became the first in league history to surpass the 1-million mark in attendance at home and away, playing before 1,045,870 fans. At Giants Stadium here, where the Cosmos play their home games, they established league records for total attendance (717,842) and average attendance (48,856).

"It's very simple: we have promoted the sport here," said Cosmos Chairman Nesuhi Ertegun. "You have to market the game. Hey, I'm in the record business. Soccer is my hobby. I'm an entertainer. Soccer should be entertaining.

"Other teams are beginning to catch up now. We took the long-range goal of selling the game and it worked. We had our problems in the beginning. We made mistakes."

The Cosmos made no mistake when they signed Brazilian superstar Pele, once considered the finest player in the world, to a $7-million contract.

"Pele started it all. He gave our league credibility and inspired other foreign stars to come here," said Ertegun. "But he's gone now and it's up to us to continue the trend. We have to entertain the people."

The Cosmos plan to remain the finest team in America by one simple means: sign the best players in the world.

Within a three-year period, Warner Communications has opened its checkbook and signed such international stars as Beckenbauer, Italian Giorgio Chinaglia, Brazilian Carlos Alberto, Englishman Dennis Tueart and Yugoslavian Vladislav Bogicevic to hefty contracts.

This year, the Cosmos added Brazilian Francisco Marinho, Iranian Andranik Eskandarian and, three days ago Dutch star Wim Rijsbergen.

"When you have money, you can get the best players in the world and that's what the Cosmos have done," said Alberto, in broken English. "They pay well. They take care of any problem the players have. Everything is done for you. I don't know about other teams but I know I would play only here because they are so organized."

However, there are rumblings that all is not well in the ranks. Players are becoming dissatisfied with their lack of playing time and are displeased that the front office has continued to sign new players. Coach Eddie Firmani has had to fine Marinho and Eskandarian for "lackadaisical play and poor conduct."

Firmani, who quit as coach of the Tampa Bay Rowdies to take the job with the Cosmos, faces the tough task of keeping the players happy.

"Right now, we don't have any big problems," said Alberto, the NASL defender of the year last season. "But I think we may be getting too many players."

Terry Garbett agreed.

"We're going to run into problems. Everyone wants to play and they can't," said the English midfielder. "We have stars at every position and some of them don't put out. It's a big responsibility for the coach and I feel a bit sorry for him."

Firmani says he does not feel any pressure.

"People expect us to win again and I feel we can," he said. "I don't think you can get too many good players as long as you get the right ones. We have a few now with suspect character and they will be disciplined. We have players from 16 different countries but soccer is an international sport. Communication is no problem."

The Cosmos have not always been successful. They enjoyed little to moderate success playing at Hofstra University, Randall's Island and Yankee Stadium. They moved to Giants Stadium three years ago and attendance skyrocketed.

"We went after certain people. We forgot about the ethnic and people over 45 and went after kids," said Don Flora, director of marketing for the team. "We sold 600 season tickets in our last year in Yankee Stadium. The next year ('77), we upgraded our advertising, promotions and sold 2300 season tickets."

Flora said they have held all types of promotions at each home game, subsidized buses to the stadium and sponsored tailgate parties. Bands, raffles and two-for-one ticket sales helped attendance immensely.

As the Cosmos started to win, the promotions were cut back. But the fans were hooked.

"We don't do two-for-ones anymore," said Flora. "We don't need to. We hope to sell 55,000 season tickets this year. We've sold 25,000 already."

All stars love the stage and Beckenbauer, Alberto and Tueart will be the first to admit playing before 75,000 fans gets the adrenaline flowing.

"All of the players here have been successful in their countries," said Tueart, a forward. "When we come here, we still want to be the best. Crowds make you want to play. Wherever we go, there are big crowds. That's good because they make the home teams play much harder."

Tueart and his teammates said they believe the other NASL teams are still basically afraid of them, particularly at Giants Stadium. Last year, the Cosmos set a league mark by scoring 88 goals, 20 more than any other team. The Cosmos scored five or more goals nine times.

They also set 20 NASL marks last season, including most consecutive home victories, 23, over a two-year period.

While many NASL people feel a third straight title for the Cosmos would be bad for the league, they admit that without the Cosmos, the NASL would be in trouble.

"It would be bad for the league if the Cosmos won again," said Washington Diplomat Coach Gordon Bradley. "It would take something away from the league."

There are also those who believe the Cosmos are not content with being the best team in the NASL but want to be recognized internationally. The front office, perhaps to help make up for its $1 million dollar payroll, sponsored a three-month tour of Europe during the winter and scheduled nine tough preseason games against foreign competition.

"Our attitude has been bad," said Beckenbauer. "We're tired. The NASL teams are much better now. We'll have to play harder."

The Cosmos' season got off to a rocky start in San Diego last Saturday night but they managed to escape with a 2-1 win in overtime.

"As long as we have the best players in the world, we'll do fine," said Ertegun, not at all unhappy with the first game. "And we'll always try to sign the best. Every year, we'll try to get two or three world-class players."

Ertegun's attitude is especially disturbing to winger Gary Etherington, the NASL rookie of the year last year.

"It bothers me that they go out and get more players," said Etherington, who signed with the Cosmos after graduating from Mount Vernon High School in Alexandria. "They've treated me well but I feel I've proved I can play in this league. I'll see how the year goes, then maybe look to play somewhere else."