Part 1: of Mice and Klingons.
Out of all the Races that we see in the Star Trek Universe I consider the Cardassians to be the most interesting both in terms of storytelling and personality.
If you compare the Cardassians to the other major non-Federation species (I'm ignoring the UFP for the time being), you can definitely see a major difference in the characterisation of the Cardassians as a civilization and as Individuals. For example if we take the most famous race in Trek, the Klingons, we can see a perfect example of how an entire Civilization can be turned from a diverse group of individuals, Classes and societies into a one dimensional walking stereotype.
The Klingons that we see in TOS are a cunning expansionist Empire locked into a Cold War with the UFP and every time we see the Klingons they are matching wits with starfleet on the front lines of this war. What is interesting about these Klingons is the way that they are presented onscreen with some Klingons having a sense of humour, a keen intelligence and some even showing a level of corwardness! These Klingons are ruthless but are willing to use their common sense when necessary and work with the Federation as required and they also engage in spying and other underhand methods to achieve their aims (perhaps it's the Human Augment in them
). In short these Klingons are a worthy counter-point to the Federation of this era. Indeed these TOS Klingons I would consider to be prototypes for the Cardassians.
Fast forward to the TNG era and thereafter and, through the power of the brain bug the Klingons have become cliche spouting, sword wielding space Vikings who randomly attack everything they come across. These Klingons are obsessed with their Honour and spend their whole lives trying to die with said honour(by killing lots of people in battle). The Klingons of this time have no tuck with garnering Intel and planing their tactics,instead launching sneak attacks and beaming into battle swords waving.
It's a shame that the Cardassian Union had to lose a war to these bozo's.
Of course I am discussing the Canonical Klingons that we see on screen; I have read KARD'S brilliant IKS Gorkon books and "A burning House" and I think that these books give the Klingon Empire a much welcome complexity.However the fact of the matter is that the Klingons have been reduced to a mono centric culture that severely weakens the fabric of Star Trek.
(As this is quite a long post I will split this essay into a number of parts each of which will examine a major Trek Civilization. Part 2 will deal with those pointy eared masters of subterfuge; the Romulan Star Empire