Maradona'a Napoli was in the era of one of the greatest sides in history with AC Milan and Juventus (although Juve didn't live upto expectations in Europe's elite tournament). Your father may say that and I would listen to him enjoying the conversation because I also witnessed that... We could have a proper debate unlike with you who didn't and only know what yo've been told or what you've seen or read. You are in my position with people like Pelé, Puskas or Di Setéfano... I know, but I have to be objective and pragmatic by looking at the whole scene around at the time.
Napoli have always been a medium type club and for much of their history (the majority), they've been a small club although not at a Benevento type level obviously.
Edit: That goes to prove how big Maradona was.