Van Gaal, who led the Netherlands to a third-placed finish in this summer's World Cup, was unveiled as United's new coach earlier this week as the Red Devils look to improve on their disappointing showing last term
The 13-time Premier League champions endured a testing season under the stewardship of David Moyes, ultimately finishing seventh as the English giants failed to mark the post-Sir Alex Ferguson era with a trophy.
However, Wenger says that the Dutchman's arrival will have England's elite on their toes once more as the "great manager" prepares for his maiden campaign.
"I believe that Manchester United have appointed a great manager who has shown during the World Cup that he's top quality," he told Arsenal's official website.
"It will certainly be difficult for us but for other competitors as well. We are all at the same level."
Van Gaal will take charge of his first game on Thursday morning as United travel stateside to face Los Angeles Galaxy.