Giggs set up two vital second-half goals for Ronaldo, who punished Arsenal's defensive frailties and established Manchester United as Chelsea's only serious challengers. United are eight points behind Chelsea, who play at Blackburn on Wednesday.
United showed their character by coming from behind after trailing twice. They even scored their fourth goal when they were down to ten men after Mikael Silvestre was sent off for violent conduct. They rarely allowed Arsenal to find their rhythm.
Usually the winners of these clashes win the championships. Either Manchester United or Arsenal have won every Premiership title since 1995. This season, they have been upstaged by Jose Mourinho's Chelsea.
But the contest still retains its worldwide appeal. The game was broadcast live in 130 countries. Hostilities began in the tunnel with words between skippers Patrick Viera and Roy Keane.
Arsenal were concerned that United would show the physical approach which rattled them in their 2-0 defeat at Old Trafford in October. The Gunners restored Dennis Bergkamp and left Jose Antonio Reyes, who was clattered at Old Trafford, on the bench.
Pascal Cygan stood in for the suspended Kolo Toure. Alan Smith was still out with an ankle injury, so United used Wayne Rooney as the focal point of a 4-5-1 formation.
United are much physically stronger than Arsenal and they are prepared to use that strength, as early bookings for Gabriel Heinze and Giggs showed.
But Arsenal made the early chances. Roy Carroll saved from Freddie Ljungberg after Bergkamp sent him through, before Rio Ferdinand blocked Thierry Henry's effort.
They went ahead in the eighth minute when Vieira outjumped Heinze to head home Henry's corner from five yards.
United levelled ten minutes later. Rooney cleverly turned Paul Scholes' pass inside and Giggs drove in a shot that deflected off Ashley Cole.
Referee Graham Poll waved away Arsenal's penalty appeals soon after as Silvestre tackled Robert Pires, before Carroll held a Bergkamp curler.
Arsenal regained the lead in the 36th minute. Mathieu Flamini took a defender away as Henry flicked Vieira's pass on and Bergkamp fired a cross shot through Carroll's legs.
Manuel Almunia's legs denied Rooney four minutes later, but Arsenal's defensive organisation is a shambles and their goalkeeper is hardly of Premiership class. They paid for it in the second half.
Ronaldo levelled in the 55th minute, nipping in behind Lauren to sweep home a cross shot after Giggs split the Gunners defence.
Three minutes later, Almunia charged out recklessly for a through ball. Giggs skipped past the keeper and centred for Ronaldo to tap into an empty net.
In between, Rooney had smacked a free-kick against the junction of post and bar.
Silvestre's dismissal for a 69th-minute off-the-ball butt on Ljungberg should have given Arsenal hope, but they failed to press home their man advantage.
Henry and Pires were peripheral and Arsenal had no plan B when their clever football was frustrated.
Ljungberg shot weakly at Carroll, Henry blazed wide and then hit an overhead shot straight at Carroll.
United wrapped it up in the 89th minute. Scholes caught Arsenal on the break and sub John O'Shea ran on to his defence-splitting pass and coolly chipped Almunia.