It's dubbed the world's most famous sports arena and since it's in one of the world's biggest cities, Madison Square Garden is again on center stage.    Chants in Friday's last session came from all corners. From Section 128, "IRAN!…. IRAN!" And usually from anywhere else "USA-USA." Pockets of fans from their own respective countries rocked and rolled throughout the first day of the World Championships of Freestyle Wrestling.    "This tends to be a tournament of momentum," Rich Bender, Executive Director of USA Wrestling, said.    That momentum can build when a line of wrestlers get hot, win matches and wins over some top competition.    Political affiliations aside, the rivalry between the United States and Iran is one of the greatest in organized sports.    Eric Guerrero's victory over Mohammad Talaei to Cael Sanderson's 8-2 victory over Majid Khodaee to the upstart 24-year old Iranian Habid Habibi defeating American Joe Williams are all part of the rivalry that's emerged in wrestling circles. Madison Square Garden, situated in one of the most culturally diverse cities in the world is an ample and willing site for this to occur.    In this arena, Willis Reed and Walt Frazier's retired numbers sit high in the rafters as do championship banners from the New York Knicks and Rangers.    Wrestling fans this weekend aren't paying as much attention to those professional sporting greats, but it's about the action and the rivalry that's on the five mats stretched across the floor of MSG.    "This is a great day for American wrestling," Bobby Douglas, U.S. world team coach said.    Wrestling aside, where the U.S. went 21-1, the crowd battles with Iran and the U.S. was only paled in comparison to the standing ovation after Sanderson topped Khodaee.    The ovation wasn't for one wrestler or the other, well, maybe initially, but for a great match wrestled.    All wrestling fans can appreciate the purity of the World Championships.    "It wasn't about the U.S. versus Iran at the end, it was about a great match," said Randall Batch, an official from South Carolina who's volunteering at the Worlds this week.      The setup, five mats lined across the floor on a raised platform, large projection television screens above each mat and monitors displaying the scores of each match.    From a fan standpoint, the tournament made every match viewable and easily followed.  "Granted I had a good seat, but my understanding in talking with people the placement of the mats was fantastic and there wasn't a bad seat in the house," Charlie Busch of Rochester, Minn. said.    "We've been working on this thing for three years. They've had a long time to get it right," Gary Abbott, Director of Special Projects for USA Wrestling, said.    Regardless of the outcomes on Sunday, New York has made a believer out of the wrestling fan that it can and will host a great tournament at an equally great venue.