Rather than rank them, I'll just toss in a few comments on the ones I've read so that you can make your own decisions, because I'm not sure what qualities you'd value or dislike.
I haven't read the Feist or the Jones; I only read about three chapters of the Keyes before tossing it (I don't recall it being grotesquely bad, just over-the-top and not brilliantly written, so not enough for me to get over a backstory that I thought was retarded), so I'll pass over those.
Kushiel's Dart -- I didn't finish this one, but read about half and will finish it at some point in the undetermined future. It is pleasantly written, far better than most fantasy novels, but not quite enough for me to call top-tier. The first-person narrator struck me as a bit of a Mary Sue with a masochistic streak, but not enough so to be really annoying. The novel's style is what I'd call the opposite of "gritty realism," even more so than GGK's work; everyone is clever, everyone is beautiful, at least in Terre d'Ange, and everyone not from Terre d'Ange is sort of pitiable and inferior.
Things that detracted from my enjoyment: a) author's setup of high-end courtesans' guilds is clearly based on wishful thinking rather than realism, research, or actually talking to anyone who does sex work; this is probably something that only I would find annoying, but I do, because it's one of those areas that writers consistently get wrong and in a novel that is all about high-end prostitution you'd think the author would do more homework; b) there's not a lot of narrative pull in the early chapters, which is partly because there's a long "development of the heroine" segment but even so I'd have liked a little more tension to keep me reading; c) waaaay too much reliance on the magical power of sex to make people blurt out information as a plot device. I know this may come as a shock, but clients don't, as a general rule, actually blurt out sensitive information in the company of call girls, much less do so consistently enough to make an entire book about it.
But overall, based on what I've read, I would consider this a good book and recommend it with some caveats that it's more of a fairytale set in a brothel than anything that even nods in the direction of realism.
The Darkness That Comes Before -- Started, didn't finish; was overwhelmed with pretentious self-important philosophical twaddle rather than, you know, an actual story. I hear this series just gets depressing later on, so I'm not especially motivated to keep jumping the story-breaking roadblocks.
Legend -- Started reading last night, am only halfway through. So far it's pretty awesome: well-written, funny, quick-moving. Gemmell hits a lot of the themes that he revisits in his later work, so it would probably seem repetitious if you read too many of his novels together, but taken on its own this is good stuff.
(I can't help wondering, though: if the invading army is so huge, why don't they just bypass the last-stand fortress and starve them out over the course of several years? The geography that makes this fortress Absolutely Crucial has not been established so far in the book, or else I missed it. Everyone just takes it as given that this will be a critical battleground and I'm like "but why? explain plz" and it isn't happening.)
The Blade Itself -- Many many people elsewhere in this forum will sing this novel's praises to the sky. I thought it was okay but not great, and haven't been motivated to pick up the later books in the series. I found the pacing off at several points, the characters unlikeable, and the plot occasionally puzzling. Finished the book not caring what happened to any of the people in it, and haven't seen much reason to find out. YMMV, obviously, or the book wouldn't have the following it does here, but I suspect dropping expectations to a human level is the best way to avoid disappointment.
Lies of Locke Lamora -- I liked this one a lot. It is a caper novel; it has all the requisite wisecracking and improbably devious plot twists and self-amused cleverness of that genre, and it is pulled off with panache. There is, however, more profanity in this book than if George Carlin rear-ended Lenny Bruce's car in hell, so be advised that Scott Lynch may make your dear old granny blush if you leave his book lying around.
