Sir Alex Ferguson described over rivals Manchester City as a "special one".
Robin van Persie's late free-kick ended the Premier League champions' 37-game unbeaten home run and sent United six points clear at the top of the league.
"It was such a good game - a special one," said United manager Ferguson of his 31st Premier League derby.
"It was engrossing. It tells you about the quality of the Premier League, it's such a great league."
However, Ferguson's side were two goals to the good inside 30 minutes, a well-taken Wayne Rooney brace giving the visitors the advantage.
After the interval City hit back with two goals from Yaya Toure and Pablo Zabaleta, before a deflected injury time free-kick from Van Persie sealed the win for the visitors.
Ferguson was full of praise for his 29-year-old Dutch forward and striking partner Rooney.
The Scot said: "It was great to see Wayne score two goals and knowing him he'll go on a run now. They were two good finishes.
"Van Persie's whole game was absolutely terrific today - he had them on the back foot."
Despite United letting their lead slip in the second-half, Ferguson was delighted with his team's intent and felt they deserved their 90th-minute winner.
"We would have been disappointed not to have won because we had played ever so well," he said.
"[City] hadn't lost at home for a couple of years and both of us are contending at the top of the league.
"There was a great team spirit and they were determined to win the match."
Manchester United are now six points clear at the top of the table but Ferguson dismissed any talk of that being a decisive gap at this stage of the campaign.
"City are fresh and out of European football," he said. "We have to contend with Europe, the FA Cup and the league. There's still a long way to go."
Rooney, who moved to five goals for the season with his pair, added: "It is fantastic. It's a great day for us, to go six clear and to beat our closest rivals.
"There is desire and passion at this club. Under Sir Alex we never know we're beaten. It's no fluke how many games we've won late on. We know it could be in injury time or in the first minute - you've got to keep on pushing."