"I think we have dominated for 90 minutes," said Van Gaal.
"It was maybe our best match of the season, especially in an away match. We deserved the victory."
Chelsea kept their lead intact by winning 1-0 at West Ham United, while second-place Manchester City, who have played a game more than the leaders, beat Leicester City 2-0.
Meanwhile, Swansea City striker Bafetimbi Gomis was said to be "fine" despite being stretchered off after collapsing on the pitch in the early stages of his side's 3-2 defeat at Tottenham Hotspur.
Fresh from victory over Tottenham in Sunday's League Cup final, Chelsea took a step closer to the league title with a win at West Ham, who have now gone six games without a league success.
The impressive Eden Hazard claimed the game's only goal in the 22nd minute with a header from a right-wing cross by Ramires, who later hit the post.
"They are the best at the way they play," said Mourinho of West Ham.
"It is not just to play football -- the pressure, the tension and the emotion. My players were fantastic. We couldn't kill the game and these three points are massive for us."
Champions City preserved the status quo at the top with a home victory over bottom club Leicester that followed painful consecutive defeats by Barcelona and Liverpool.
City, who dropped out-of-form captain Vincent Kompany, took the lead in first-half stoppage time when David Silva followed in to score after he and Wilfried Bony had seen shots blocked.
James Milner sealed victory two minutes from time by smashing home a cross from Jesus Navas.
Third-place Arsenal also won, prevailing 2-1 at third-bottom Queens Park Rangers to remain four points below City.
Olivier Giroud poked home a cross from Kieran Gibbs in the 64th minute and Alexis Sanchez doubled Arsenal's lead with a solo effort five minutes later - his first goal in eight games -- before Charlie Austin replied for QPR.
Liverpool extended their unbeaten run to 11 matches by overcoming second-bottom Burnley, taking Brendan Rodgers's side back above Southampton and into fifth place.
Jordan Henderson followed his stunning goal from Sunday's 2-1 defeat of City with a 29th-minute opener from the edge of the box and then teed up Daniel Sturridge for a 51st-minute header.
Ki Sung-yueng equalised for Swansea in the 19th minute, but second-half goals from Ryan Mason and Andros Townsend were enough to give Spurs the win despite a late effort from Swansea midfielder Gylfi Sigurdsson.
Meanwhile, Victor Moses and Mame Biram Diouf scored as Stoke City beat Everton 2-0.
-AAP
