none of them are. thats why they are all just flash in the pans. and its precisely because they arent as rich as arsenal that they dont have the longevity that arsenal have had in this tournament over the past couple of decades.
deportivo, valencia, roma, panathanikos, galatasaray, porto, us etc etc, have all finished above arsenal at some point in the champions league over the past couple of decades. but just like dortmund, shakhtar, schalke etc, they dont have the extensive champions league history that arsenal have. basically, given the high number of teams of this relative size in the champions league (compared to arsenal), its no surprise that some of them finish above arsenal in the champions league every year. just like its no surprise that arsenal have finished above man utd, real madrid, barcelona, ac milan etc etc too at times.
this is a knockout competition, and just like people always do in football, too many wrong conclusions are being made in the heat of the moment.