I actually like some of the SW designs in particular the Star Destroyer is a fantastic example of an iconic vessel. (although the bridge is a wee bit exposed...)
Just a bit.

(Not that Trek bridges
aren't.)
Don't the Cardassians have a different warp design than most other powers since their nacelles seem to be swept forward and closer to the main hull, which creates a smaller more effective FTL field?
Good point; they're one of the examples that deviate a bit further from the "base design" than usual, but it's still the familiar "twin glowing nacelles, one mounted on each side of the hull" business.
Oh, and I think the Cardassian design is to strengthen the structural integrity field by making the ship more compact - how they compensate for increased radiation exposure or the like I don't remember...
There was no
canon explanation, of course, since no one wrote in any dialog touching on pulled-in vs. suspended nacelles. I seem to recall the tech manual saying that the efficiency (or lack thereof, compared to suspended nacelles) of the warp field was one of the
disadvantages of the pulled-in design. Still, I'll have to check when I'm home; I can't remember
what it said with any certainty, and now I'm curious... Not that tech manuals are definitive authorities by any stretch, but they can at least provide a place to start speculating.
Oh, there's no doubting the awesomeness of the Imperial Star Destroyer. But I never liked the overall ship aesthetic in Star Wars.
I always thought the SD was pretty good, but not great. It certainly has the intimidation factor (which, in-universe, is kind of the whole idea), but simply in terms of my personal sense of starship aesthetics, it actually never did that much for me. I thought some of the Mon Cal cruisers were pretty nice looking, though.
I think that the Cardassian base design for the Galor type warcraft follows the basic design ethic of a paranoid expansionist military dictatorship, low center of mass to prevent easy targeting, smaller more workman like constructions and of course an intimidating profile. (although your mileage many indeed vary on this)
It makes sense for the Cardassians; especially if one of the downsides IS a less efficient warp field, it fits for them to trade that for a ship that is more rugged and durable. Actually, that seems to be a thing with Cardassian ships in general. Technologically, they are pretty unimpressive, and their offensive capabilities don't seem to match up to most of the other major powers. On the other hand, they can take a freaking
pounding. Kind of the opposite of Klingon ships, really.
Visually... the Galor-class does look tough to some degree, but it also looks like a shrimp to me, reducing some of its potential intimidation factor.
This is something that I felt was a major issue, and one that really got on my nerves with Star Trek, for exactly the same reasons you described. The re-use of ships-of-the-week, in many cases without any modifications, made ST look cheap and unrealistic at times. And before the excuse is waved that the budget couldn't accomodate new models, I just have to say that Classic Doctor Who, which had a shoestring budget, never re-used a single spacecraft model in the 25 years it was on television, with the exception of Nerva Beacon, which in the two episodes it was featured in, was meant to represent the same station, only at two different points in time.
I agree that it would have been very
nice to see a greater variety of "alien of the week" designs. However, with regard to budget and the comparison to Dr. Who, don't forget that a show on a limited budget must pick and choose where to spend ever precious dollar (or whatever unit of currency). More unique designs showing up might have meant crappier something-else.
I don't know why they just couldn't have used the unmodified Voyager model anyway.
It was a kitbshed model meant to be seen only in the far background, and not meant to be taken seriously.
Yeah, it was never seen up close. The DS9 tech manual kind of made it
worse all around, by showing it in detail, and explaining it
in-universe as a kitbash (and of course, it wasn't the only such ship). Never liked that.
As for the original question, a ship that made me go "WTF", I have only one thing to say: Freedom class.
http://www.trekmania.net/the_fleet/utopia/others/freedom.htm