Ah right, with you.
Reasonably popular yes, but oddly enough, not in Manchester. Most Maccans are supporters of Manchester City, who are by comparison, a very mediocre team. A few years back when they won the treble of the Premier League, F.A. Cup and the UEFA Champions League they were touted as the greatest team in the world. To be honest though Real Madrid are better in Europe.
Man Utd are a bit strange in that people either support, or loath them. The general consensus is that referees officiating (especially at Old Trafford) are biased in their favour. Before Utd's rise to glory under Alex Ferguson (who is it has to be said, a brilliant football mananger, even if he is a complete ******** of a human being) Liverpool were the dominant English team. As a Man Utd Fan I loathed Liverpool with a passion (the two teams always have had a great sense of rivalry) and detested the way referees were biased towards them and that they recycled their crowd's noise through the PA system to magnify it. They were also a bunch of dirty, cheating bastards. However, non-Liverpool supporters (who weren't ManU fans) had a great respect for the club, totally unalike how Manchester United are regarded.