Like most folks, I split
Castlevania into its classic and
Metroid-ish incarnations. Ironically, there's a little bit of exploration in
Rondo, which may be why its reputation is pretty good. Well, that, and it's a really solid game. Is it mind-blowing, though? Not particularly.
I'm not sure, though, which game in the series that I'd put on the top of the heap. Almost all of them have some attribute that I like that the others don't have, and it makes it hard to choose a clear-cut favorite.
SCIV is indeed great, though, and I love the multi-directional whip. I also like that it's got teeth, but not to the level of its forebear. (Seriously, the US release of
CVIII is tough stuff.)
Rondo is actually a strikingly easy game. Well, easy if you use Maria, anyway.
I've got big hands, but I don't really like the Duke. I don't think it's so much a size thing as a placement thing for several of the buttons. It just feels off to me. That, or it fits my hands too well and makes things all gross and sweaty. I like a little air.