Manchester outclassed north London in a Premier League goal frenzy Sunday as United thrashed Arsenal 8-2 and City thumped Tottenham 5-1 in a pair of rampant attacking displays.
After Edin Dzeko's hat trick helped City dominate at White Hart Lane, Wayne Rooney responded with a treble of his own as Arsenal allowed eight goals in the league for the first time in 115 years.
"You feel humiliated when you concede eight goals," Arsenal manager Arsene Wenger said. "It was a terrible day for us, it was a combination of an under-strength team and weakness."
Arsenal has just one point after three games and has seen a player sent off in each match, with defender Carl Jenkinson dismissed against the league leaders.
"The performance today was incredible and we deserved the result," Rooney said. "Whether or not Arsenal have a full-strength squad, every time we play them we have a go and try to score. They had some players out but that should take nothing away from us."
United tops the standings on goal difference ahead of City as the only teams to have opened the season with three successive wins.
Tottenham, though, is stranded at the bottom after being ripped apart by big-spending City.
"Today was something special for me, to score four goals in the Premier League is fantastic," Dzeko said. "I think we're getting better and better."
Also Sunday, Leon Best's second-half double clinched a 2-1 victory for Newcastle over Fulham and Ryan Shotton's late goal gave Stoke a 1-0 win over West Bromwich Albion.
At Old Trafford, United scored eight goals for the first time since 1999.
It was Danny Welbeck who netted the first, heading over Wojciech Szczesny in the 22nd minute before later coming off with a hamstring injury.
Ashley Young doubled United's lead six minutes later with a curling strike just after Arsenal captain Robin van Persie missed a chance to equalize when David de Gea turned his penalty wide.
Rooney netted his first just before halftime with a perfect free kick landing in the top corner, but Theo Walcott pulled one back in stoppage time to reduce the deficit to 3-1 at the break.
There was no recovery, however, with Rooney restoring the three-goal cushion in the 64th by curling another free kick past Szczesny.
Nani chipped in another three minutes later before Ji Sung-Park found the bottom right corner to make it 6-1.
Even after van Persie pulled one back, Arsenal's misery continued with Jenkinson sent off with 14 minutes to go for hauling down Javier Hernandez, having already been booked.
Rooney was able to complete his hat trick in the 82nd from the penalty spot after Walcott fouled Evra, taking his United tally to 152.
"When you play Arsenal you expect a difficult game," United manager Alex Ferguson said. "We got careless at times and they made chances because they still have quality up front, but overall we are very satisfied that we kept the performance levels up."
And the performance overshadowed City's ruthless display at Tottenham earlier in the day, inspired by a lively Samir Nasri on his first appearance since moving from Arsenal.
It was the France midfielder who provided the 34th-minute cross that Dzeko tapped home for City's first goal.
Tottenham could have quickly leveled when Bale delivered a crisp cross to Crouch, whose downward header crept wide.
City's second took goalkeeper Brad Friedel completely by surprise, remaining static as Dzeko buried another cross from Nasri into the net with a header.
Yaya Toure supplied Dzeko's third 10 minutes into the second half, while Sergio Aguero netted after bursting into the box past Michael Dawson.
Younes Kaboul pulled one back for Tottenham, but Dzeko put the gloss on City's win in stoppage time by curling the ball into the top corner.
"This is a very long season and it's important that we started well," City manager Roberto Mancini said. "The next games will be very hard because now everyone thinks we will score three or four goals, but that is impossible."
At St. James' Park, Best tapped in Newcastle's first at the start of the second half after Yohan Cabaye's shot rebounded back off the bar before grabbing his second with a poked shot from 12 yards (meters) in the 66th.
United States midfielder Clint Dempsey's 88th-minute header from Danny Murphy's free kick ensured a tense finale but Newcastle held on.
The Stoke-West Brom match was heading to a draw until Jonathan Walters pumped a harmless ball into the box and West Brom goalkeeper Ben Foster and center back Gabriel Tamas allowed Shotton to nip in and score in the 89th.