Its such a subjective question everyone has different criteria.
For me the clubs history is important, but modern history will always outweigh a clubs achievements before that and the longer so the less weight of attach.
Support is relevant, of course.
Trophies and consistent competitiveness counts, both domestic and European.
Ultimately the current standing and performance of a club has a big influence, albeit that can change quickly.
I think there's a group of around a dozen clubs that you could select from, but narrowing it down is practically impossible.