Park Ji-sung gave the Red Devils an early lead when he converted after good work from full-back Patrice Evra.
The struggling visitors saw striker Conor Sammon shown a straight red card by referee Phil Dowd for raising his arm as he backed into Michael Carrick just before the break.
United soon made their advantage count as Dimitar Berbatov (40) doubled the lead, with the Bulgarian netting again just before the hour.
Winger Antonio Valencia knocked in a fourth with 15 minutes left, before Berbatov completed his hat-trick from the penalty spot (77) after Antolin Alcaraz had fouled Park.
City, meanwhile, were left frustrated at The Hawthorns, where Mario Balotelli had an effort chalked off for offside after 33 minutes as the home side battled to a well-deserved point.
Chelsea's title hopes suffered another heavy blow as Fulham came from behind to consign them to a third successive 1-1 draw.
Fernando Torres flopped on his first league start for almost two months, although he did inadvertently lay on Juan Mata's 47th-minute opener, the winger's fifth goal of the season.
Fulham belied their miserable away record to equalise nine minutes later through Clint Dempsey's ninth of the campaign, ensuring the spoils were shared in the west London derby.
Bottom club Blackburn earned a 1-1 draw at Liverpool, where stand-in goalkeeper Mark Bunn produced an outstanding display.
Reds midfielder Charlie Adam put the ball into his own net on the stroke of half-time after a corner from Morten Gamst Pedersen to give Steve Kean's men a shock lead.
However, the home side rallied after the break, and were level through Maxi Rodriguez (53).
Despite plenty of pressure and the return of captain Steven Gerrard from a two-month absence with an ankle infection, Liverpool could not conjure a winner past inspired Rovers number two Bunn, who denied Andy Carroll again in stoppage time.
Sunderland had to be content with a point against Everton, who equalised with a controversial second-half penalty at the Stadium of Light.
The Black Cats looked on course to continue their revival under new boss Martin O'Neill when Jack Colback's 26th-minute effort deflected over keeper Tim Howard off Sylvain Distin to give the 22-year-old midfielder a first senior goal.
However, the visitors were back in the game when World Cup final referee Howard Webb pointed to the spot on 51 minutes after Leon Osman tumbled in the box despite there appearing no contact, Leighton Baines smashing home the resulting penalty.
Two goals in as many minutes from Hatem Ben Arfa and Demba Ba earned Newcastle their first win in seven league games against struggling Bolton at the Reebok Stadium.
The Magpies had taken only two points from their previous six games while Bolton's victory over Blackburn in midweek ended a run of five straight defeats, and in the first half it appeared very much a battle between two struggling sides.
But the deadlock was broken in the 69th minute when Ben Arfa netted his first goal in more than a year and the prolific Ba doubled the lead soon after.
In the late kick-off Stoke drew 0-0 at home to Aston Villa with Emile Heskey hitting the woodwork in the first half for the visitors and Marc Wilson heading against the bar after the break.
Monday's Premier League Results
Chelsea 1-1 Fulham
West Brom 0-0 Man City
Sunderland 1-1 Everton
Bolton 0-2 Newcastle
Liverpool 1-1 Blackburn
Man United 5-0 Wigan
Stoke 0-0 Aston Villa