I recently caught half an episode of DS9 on German tv (on a side note, HILARIOUS to watch it in German even if you dont understand it), it was the one where Martok takes over command of the empire and fleet once Worf lays the smark down on Gowron.
And I got in a very stilted cinversation with one of the Germans I lived with, he was saying (or I think he was) that the Klingons are the most well rounded species we see in Trek, with the most effort put into building them up as a culture.
I was arguing for the Cardassians as we have at least seen different sorts of Cardassians and seen them function as a society that is semi believable.
The three species we see the most of (that arent Federation members) are the Klingons, Romulans and Cardassians. I personally think that while we see alot of the Klingons, they are very 2 dimensional. The Romulans only slightly less so due to the Tasha Yar half Romulan clone plotline in TNG and the Cardassians the most.
All other species fall far behind as we dont see many other species show up over several series or seasons.





