I like both the 3D and the 2D games, there is just no way to compare them. Even if 2D is not something new and 3D seems more "real" 2D is just something special on it's own, something 3D can't achieve.
Back on topic:
I voted 3D CV64/LOD
why? I loved the fact that castlevania 64 had both exploration and platforming combined. What I'm hoping to see is something along the same lines in game play, better controls, more re playability (was already a plus point in castlevania 64 since they had actual alternate stories), and an improved horror factor.
The last one might not be obvious to most people.
The great thing about castlevania 64 is in one word: Malus, the kid freaked me out. Did then and still does now. If Dracula is the lord of darkness and stands for about anything evil and dark, I'd be realistic for him to hoard horrors that even make Belmonts turn in their sleep.
I'm not saying that castlevania should be transformed into a horror adventure, I'm just saying that a little bit more of the horror factor implemented would increase the whole awe of castlevania itself. No longer just a pretty looking castle but an actual creature of chaos.