Manchester City's new stadium has a capacity of 48,000 and sells out most games. In fact, and contrary to what has been written above, getting a ticket for any Premier League game is problematic at best, and impossible at worst. To put it into context, City's old ground held 34,500 and was full every week. The new ground holds 14,000 more, but they now have 37,000 season ticket holders!
As for the capacities, one thing that needs to be borne in mind is that all the grounds are covered, naturally enough because of the weather, and that reduces the feasible capacity substantially. The truly huge football grounds (i.e. 120,000) tend to be open air. Man United could easily fill an 80,000 stadium every week, Arsenal, Liverpool and Newcastle a 65,000 one, Manchester City, Everton a 55,000 one and so on.
She's as nervous as a very small nun at a penguin shoot.