I don't think I've ever played a Castlevania game. Wii U VC has many of them, which one is recommended to start?
There are two styles of castlevania games.
The games on (S)NES and other consoles are punishing, linear platformers with limited character mobility that require you carefully time your jumps and attacks.
The games on GBA and NDS (and Symohony of the Night) are quick action games that usually require you to explore a big castle. The difficulty is way lower and there's an emphasis on RPG elements; levelling up, switching gear. This games fit under the metroidvania label.
Out of the classic Castlevania games I've played (I, III, The adventure (GB), Rondo of Blood and it's remake) I like III the most. It has multiple paths and partners, so there's replayability and the level design is really varied. I was super impressed that such a modern feeling game came out so long ago. Be warned though, the game is hard, like really hard, so I'm hesitant to recommend it as your first classic Castlevania.
That's why you should probably start with Rondo of Blood (only available in Wii mode so far). If you have a PSP or Vita (NA only), you could instead get Dracula Chronicles X, which is an uglier but otherwise superior remake of Rondo of Blood. You can also unlock the original version and Symphony of the Night.
Speaking of Symphony, many say that it's the best metroidvania but to me that's just nostalgia talking; the game lacks challenge to the point of being boring. Aria of Sorrow is my favorite out of the metroidvanias and I've played them all except Circle of the Moon which supposedly more closely resembles the classic games than other metroidvanias.
The original NES game is also enjoyable but kind of basic and short.
The GBA and DS Castlevanias are just inferior versions of Symphony of the Night. Dawn of the Sorrow on the DS is probably the most worth playing. I don't think that's made it to the Wii U yet but DS games are supposed to be coming. The GBA Aria of Sorrow is also fine if you really want to try out this style of Castelvania on the Wii U right now.
Maybe if you're wearing nostalgia goggles. Symphony was the only metroidvania I had to force myself to finish; the game is just that boring.
Aria of Sorrow is hands down the best Metroidvania; the soul system just adds so much variety.