Victory against West Ham at Upton Park on Wednesday night could see United extend their advantage at the top of the table to 18 points and all-but confirm a record 20th English top-flight title.
Allardyce confessed he has been in awe at the way Sir Alex Ferguson's side have gone about their business in the Premier League this season.
"I think you have to say the United team is as good as it has ever been because nobody normally wins the title so easily and by so big a margin, or has this much of a margin at this stage of the season," he said.
"It is pretty scary what total they might actually finish with.
"Manchester United have been outstanding and their squad rotation has been Sir Alex's masterpiece as usual, about playing the right team at the right time.
"They have not had the normal focus on three or four competitions almost to the end, the focus has come on the Premier League and they have just breezed it.
"They have just gone 'bang' and everyone else can't get near them."