NEW YORK, SEPT 14: Andre Agassi rules. That alone should indicate how fragile the state of men's tennis is these days.Agassi's 6-4, 6-7 (5-7), 6-7, (2-7), 6-3, 6-2 triumph over fellow 29-year-old American Todd Martin in Sunday's US Open men's final closed the millenium on Grand Slams and lifted Agassi to world number one.Agassi won in three hours and 23 minutes to take $750,000. It was the first five-set US Open men's final since Mats Wilander beat Ivan Lendl in 1988 and only the third final here in a quarter-century to go the distance.``How can you ask for anthing better than two Americans in the final of the US Open playing a great five-set match?'' Agassi said. ``Win or lose today it was truly a privilege and an honor for me to be out here. These are the greatest times of my life and I will never forget New York.''Agassi completed a rise from 141st in the world in 1997 that included a runner-up finish to Pete Sampras at Wimbledon and winning the French Open in June to become the fifth man to complete a career Grand Slam.Yet, while teens dominate the women's field, the top men these days are older stars who have spent more than a decade leading their game, an older generation keeping youngsters at bay for one more day in the sun.``The women are young and they are going to get better,'' Agassi said. ``Us guys are kind of tapping into something that we, somewhere in the back of our minds, believe won't be around too long.''Asked what he would have said if someone had told him at his low point that he would capture two Grand Slam titles in 1999 and just miss a third, Agassi said, ``I would tell them to stop smoking the crack pipe.''While Sampras has spent six years at the top, Agassi seeks his first year-end number one finish after a career that careened from domination to free fall and back again. Missed opportunities do not worry Agassi.``I don't know if you ever really make up for missed opportunities,'' he said. ``The best you can do is not live in regret. But it is nice to actually get another shot at it.''Agassi said his periods in the tennis wilderness not only enhance his success, they made it possible. ``Part of me is convinced that if it wasn't for those valleys, these peaks wouldn't be this high,'' Agassi said. ``It's how my spirit has always worked. And, secondly, I think there has been a lot of gain I've received through those valleys. I've always found a way to get the most out of my life.''Capturing a US Open title in front of fans who have watched the twists and turns of his career and hairstyles for more than a decade must have been special. ``They've watched me grow up,'' was Agassi's simple explanation for the affection shown him by the US Open fans.``It's hard not to care, on some level, when you watch somebody develop from a teenager who says and does a lot of the wrong things to a person who gets out there and appreciates the opportunities.''``What I missed out on for a few years in my career I can never get back,'' said Agassi, whose first US Open win in 1994 came when he was an unseeded player working his way back to the top after falling out of the top 20 in late 1993.``I don't know if you ever make up for missed opportunities. The best you can do is not live in regret from here on in. That has been my commitment, that if I do lose, or if I do miss out on certain opportunities, that I don't regret not at least being prepared and taking my fair shot at it.''Agassi started his rebuilding at ground level, returning to the challenger circuit in 1997 in a bid to gain some match confidence. In 1998, he made the biggest one-year jump into the top-10 in the history of the rankings, from 122 to a year-end ranking of number six.Serena doubles upFor her encore to the US Open singles championship, Serena Williams played some more tennis, and won another title. This time, she brought her big sister along.Venus shared the glory with Serena on Sunday as the Williams sisters defeated Chanda Rubin and France's Sandrine Testud 4-6, 6-1, 6-4 for the women's doubles championship.But the crown seemed to provide no great comfort for theolder sister.Venus was still showing the disappointment of her semifinal loss to Martina Hingis as her sister celebrated almost $1 million in earnings from the final two days of the tournament.Serena joked about the tax bite on her prize money and how she should have talked about that with president Bill Clinton when he called to congratulate her. All the time, Venus looked almost glum.