@Radish & Yoshiya
I would highly recommend buying one of the three DS Castlevanias (preferably "Dawn of Sorrow" or "Order of Ecclesia". "Portrait of Ruin", while still a great game, isn't as great as the other two). They were directed by Koji Igarashi, and are going to be a different style that what we're going to get with "The Mirror of Fate", which will be directed by David Cox.
I'm a huge fan of Iga-Vania/Metroid-Vania (which started with Symphony of the Night, and as the name implies, is very similar structure wise to 2D Metroid). But there's other styles of Castlevania.
1. Classic Castlevania (Predominantly on the NES and SNES, ended with Super Castlevania IV. Level based side scrolling action titles.)
2. Iga-Vania (Developed by Koji Igarashi and is inspired by 2D Metroid. Started with Symphony of the Night on the PS/Saturn. Last entry was Order of Ecclesia on DS)
3. Mercury-Vania (Developed by Western-based MercurySteam. More 3D focused and started with Lords of Shadow and is suceeded by Lords of Shadow 2 and Mirror of Fate)