because of their fanbase? or there turnover? and Inter haven't won it for 40 years Rimbo!
The thing is, though, "big" or "top" club is such a vague term. If we judge it on footballing ability and what-not first and foremost, then the five teams I've mentioned would all give Arsenal a match. So then, you have to define more criteria to rank them. I'd put history next, in which case them five teams all eclipse Arsenal.
Not only that, Inter, Real, Barca, United and Bayern all have global fanbases the size of Arsenal's, if not bigger! They're global brands. United, Real, Barca and Bayern are clearly "topper" or "bigger" than Arsenal, and I'd say Inter are too.