I’ve read a decent chunk of all of the Conan stories, by all of the Conan authors, and I enjoyed all of them.
Howard is uneven: His best are brilliant, but a lot of them are like a caricature of the best. That makes sense when you consider he was writing for a living, and churned out stories to pay bills. I think I enjoy the atmosphere the most, the mixture of adventure and horror set against the background of the Hyborian Age. That’s definitely a big part of the reason I play this game - the chance to play in the world that Howard created.
Carter and de Camp have some good stuff: I enjoyed the novelization of the Arnold movie, and the first actual Howard stories I read were collections that they put together with pastiches to tie the stories together. Their original stories utterly lack Howard’s gift for gritty realism, but they’re still fun.
Jordan’s stories are pure formula, and if you’ve read one you’ve read them all. It’s literally the exact same story with different settings and names, every single time. What I most enjoyed are the novel length treatment, and the quality of the writing - especially the first time I read one. But I didn’t find any of the elements that define Howard’s best work. Conan doesn’t brood, there is neither grit nor realism, and you’ll find more atmosphere in a half-deflated balloon.
I’m glad I read all of them, but the only stories I still re-read are Howard’s.