Well if the Facebookers have their way, it would be SotN.
Seriously, the Castlevania page will have something about a boss from Castlevania 4 or something, and there will be a bunch of people commenting on it, with a stupid "You should remake SotN!!1!1". Those comments don't even have a thing to do with the picture! I should stop reading those. It's like Youtube comments: I just need to teach myself to stop reading them, and life will be far less annoying.
Anyway, yeah 3 would be one kickass remake if done well. It'd be neat to see a bunch of cool stuff added to 2 as well. Maybe more weapons, more bosses, more songs for larger open areas, different themes for each mansion... Yeah.