Harmony of Despair is pure fan service, and my favorite Xbox Live Arcade game. I've probably poured more hours into that game than any other Xbox game not call Mass Effect 2 or SSF4. The sheer amount of depth to it is amazing (if you're okay with repetition), the DLC is challenging, and it's just loaded with fan service. I might even get it again for PS3 just for the offline co-op! Oh, and I main Maria Renard and Julius Belmont, with Charlotte in there sometimes for variety
As far as the rest of the series goes, it's easily one of my top ten favorite gaming series ever. I've played more or less all of them (yes, including the obscure ones like Rondo Of Blood and the original Gameboy games.) It's been one of those series I've been playing since I was 6, starting with Super Castlevania 4, and it's just always appealed to me. To be honest though, I wasn't wild about Lords Of Shadow. I don't know what it was about it, maybe the stale 3D Beat-Em-Up formula it followed? It's unfortunate seeing as I was so looking forward to it. Regardless, Castlevania is an amazing series