Lepin (rebranded to King) sets are very high quality, although Technic pieces can be a bit too loose or too tight. Decool is supposed to be better for Technic pieces. Bela is similar to Lepin / King. All three brands produce only clones of LEGO sets as far as I know.
XingBao is owned by the same company that produces Lepin / King sets, but all their sets are original designs. The quality is the same as that of Lepin / King sets.
Sembo is a pretty decent brand for smaller sets and sell mostly original designs. They do have some bigger sets, but those aren't the same quality, design-wise, as XingBao.
Quan Guan has some excellent military themed sets that look very similar to sets sold by Polish brand Cobi, although they aren't direct clones. Unlike aforementioned brands, however, these sets do contain some parts that don't have a LEGO equivalent.
Kazi & Englighten also produce some excellent military themed sets, although the brick quality of Kazi is not as good as that of the other brands in my experience.
Gudi's also pretty good for (original design) girly sets, similar to LEGO's "Friends" theme.
Most of the Chinese brands are pretty decent, really. There's a few bad apples here any there, but in my experience those are the exceptions rather than the rule.