Back-and-forth went two of the top young stars in the Eastern Conference: Ovechkin, Washington's back-to-back Hart Trophy winner, against the Flyers' blossoming young captain.
Richards bested Ovechkin in goals -- and on the final score.
"There's no doubt it's fun once in a while," Briere said. "I think it's exciting. It's great for the fans. I certainly think it's good for the game."
Richards had his second career NHL hat trick to help the Flyers improve to 3-0 for the first time since the 1998-99 season. Ovechkin scored twice and has five goals already in three games this season for Washington (2-0-1).
"It's not the ideal way to win, but every once in a while you have to find a way to win these games," Richards said.
Matt Carle set a Flyers record among defensemen for most assists in a period with four in the second.
Alexander Semin also scored twice for the Capitals.
"We don't want to get involved in a track meet with the Pittsburghs and the Washingtons of the world," Flyers coach John Stevens said. "I think we're built just a little bit differently, but we do have an exciting offensive team and I think you saw that."
Ovechkin and Richards turned the second period into a rapid-fire game of 1-on-1 that gave a sold-out crowd at the Flyers' home opener its money's worth.
After a scoreless first, Richards took a fantastic pass from Carle and shot high from the red line 1:37 into the period for the power-play goal to make it 1-0.
The fans were just winding down from the replay when Ovechkin, who scored twice on opening night, scored his first goal thanks to a turnover and tied it only 67 seconds later.
Ovechkin made it 2-2, and Richards had another goal on the power play that tied it at 3-all.
Ovechkin appreciated going goal-to-goal with Richards.
"He's a great player and this was a great game," Ovechkin said.
When Richards scored his third goal of the period only 18 seconds after his second and put it past Varlamov, the crowd burst into cheers. Fans littered the ice with hats and caused a brief stoppage. Richards pumped his fists and was mobbed by teammates after giving Philadelphia a 4-3 lead.
The Flyers collected 492 hats.
"You definitely enjoy the rush," Richards said. "You have to do that when you get the opportunity."
No one played a bigger role in Richards' success than Carle. The defenseman forced the turnover that led to Richards' third goal. Carle had two points in the first two games.
Semin tied it at 4 early in the third, and Brendan Morrison put the Capitals ahead when the puck bounced off him and past Emery as he skidded into the crease.
Scott Hartnell poked in a deflection with 4:10 left in the third that gave the Flyers new life and would sent the game into overtime. The goal was Philadelphia's third on the power play.
Emery, who had a shutout in his Flyers debut, was shaky in his first game in front of the orange-and-black clad fans. He stopped 31 shots.
Varlamov allowed four goals on 25 shots.
"Varlamov has to be more mentally tough to play," Capitals coach Bruce Boudreau said. "They seem to score in bunches on him right now."
Briere, who missed most of last season due to groin and abdomen injuries, bailed out Emery with his first goal.
- Flyers general manager Paul Holmgren said C Blair Betts will miss at least a month due to a dislocated right shoulder. Holmgren said rookie LW James van Riemsdyk had his "bell rung" and will be evaluated on Wednesday.
- Washington RW Mike Knuble, who spent the last four seasons with the Flyers, got a nice ovation during pregame introductions.
- Richards' previous hat trick was Feb. 8, 2006, against the Islanders.
- Richards tied the Flyers' record for most goals in a period.
- The last defenseman to record four assists in one period was Los Angeles' Rob Blake, who did it in the second period against Calgary on Jan. 29, 1998.
- Richards was the first Flyers player to post a hat trick in the team's home opener.