Some evidence below. In all cases the US cover is on the left, UK cover on the right.
The US covers for the Mercy Thompson series are gorgeous. I know there are people who like the UK covers, but to me when compared to the stunning US ones they are kind of yuck. As I love the series I have to find the US covers. Some of the UK urban fantasy covers are just so ugly and rather generic.
For the Kim Harrison series when the books started being published in the UK I kind of stopped getting them. Seriously, I think if I'd still been able to get hold of the US covers easily I would probably have continued with the series. As it is I think I stalled out at book 4. That book is still on my TBR pile, but I've kind of never got round to reading it and book 5 languishes on my Amazon wishlist.
This doesn't just have to do with the book covers, though when they are that yellow it doesn't help. When you're in the UK and are into a US series, when a UK publisher comes along and buys the series you're happy that it's good news for the author. But in general the publisher then f*cks up the relationship the reader has with the series. The number of series I have stopped reading because a UK publisher gained the rights - Jim Butcher's Harry Dresden series, Charlaine Harris's Sookie Stackhouse, the above mentioned Kim Harrison's series. :sigh: but I guess that's a post for another day. Back to the yucky covers.
The Working for the Devil cover illustrates what I mean by generic. If you removed the author's name from the cover, this could easily be a UK cover for a Kim Harrison book.
And, okay, I get it, they've given urban fantasy an identity on the bookshelf at Borders. But it's such an ugly one.
Compare the three US covers, they are all unique. And whilst the Working for the Devil cover is not one of my favourites, I'd take it over the blah blah look of the three UK covers any day.
But, I admit, there are always exceptions to any sweeping generalizations I may make. :) I love Kelley Armstrongs UK covers. They've given the series a strong identity, but are individual to each book and not blah.
And for gorgeous painted covers, you can't get much better than the UK Gollancz covers for the Warprize series by Elizabeth Vaughan. I do like the US cover but the UK one is just beautiful.
Anyone have any others they'd like to share?