Legend of Nereid, Immortal Regis (and sequel), Vinland Saga, Beelzebub, Deadmans Wonderland, Demon Diary, Kurozakuro, Ares, Blazer Drive. Those aren't animated yet.
For yaoi/shounen-ai/BL genre the there is Finder Series and Animal X, that could be animated for a longer series. *hopeful*
I'd like to see more long series from the BL front, compared to the short OVAs and miniseries tradition going on now.
For example Mirage of Blaze has massive amounts of novels writen for it, and they reduced it into an 13 ep miniseries + 3 OVAs. Without seemingly wanting to continue it anymore... that sucks.
Vice versa with Loveless. And both titels are popular. Why do not continue? *muttering*