Ronaldo's goal came after a feed from substitute Louis Saha found Patrice Evra alone on the left side of the box. Evra delivered a cross to a wide-open Ronaldo for the finish.
The tying goal resulted from some inspired play by Cesc Fabregas, who cut the United defense in half and had his shot saved by Edwin Van der Sar.
The rebound bounced to Gallas, whose try initially appeared to be saved again by Van der Sar. Fortunately for Arsenal, the linesman's flag was up to indicate the ball had crossed the line—and replays validated the call.
The first half was disappointing, as both teams came out tentative. That changed just before the halftime whistle, when a cross from Ronaldo found Wayne Rooney, whose tap-in caromed off Gallas' leg and into the net.
I'm not sure I agree with the official scorer's call of an own-goal, but in any event the game was on.
Fabregas scored in the third minute of the second half to even the score and set up the fantastic finish. The teams traded chances in the second half, but it was Arsenal with the better of the play.
Shot attempts favored Arsenal 17-10. The Gunners were on-target only six times; United only four.
On the whole, I was impressed by the young talent on both squads. There's no doubt Ronaldo and Fabregas are two of the best in the world right now.
Both teams will be happy with the point—Manchester United because it came away from home, Arsenal because they snatched a draw from the jaws of defeat.
Arsenal and Man U both play Champions League games midweek. Victory would qualify either team for the knockout stage of the tournament with two games left in the Group stage.