No one cares about Scottish football anymore But back when they did, United-Celtic definitely had more of an affinity than United-Rangers. Firstly there is the religious aspect. Every time this is brought up, people debate this and say United aren't and never were a Catholic club, which is true, but they seemed to have a larger Catholic following. For starts, Manchester City was formed as a St Marks COE church team (All men were welcome to join, regardless of religion). Maybe that explains why the Catholic communities were more drawn towards United? Much was made of Best being protestant, but that much was made of it tells you something in itself. (although he supported a United Ireland football team) Thankfully all that is resigned to the past. Then you look at the fact that Manchester United and Celtic were successful at the same time. Celtic won the European Cup in 1967. United won the European Cup in 1968. The two clubs have hardly ever played each other, so there isn't really a rivalry between them. More recently Henrik Larson was a Celtic Legend and briefly a Manchester United fan favorite. Then you have Rangers trashing Manchester and stopping United getting a parade for their European double.