Upon close inspection of two newvideos of the WiiWare title, Castlevania: The Adventure ReBirth, we can confirm the following: It's definitely a Castlevania game. While the game is a remake of the Gameboy title of the same name -- sans the "ReBirth" bit -- the WiiWare version is more reminiscent of the 16-bit games found on the Super Nintendo and Genesis. In fact, we're fairly certain we spotted some reused art from said 16-bit games, which is pretty characteristic for a Castlevania title! Still, the classic monster-slaying, holy-water-tossing gameplay looks to be firmly intact.
I would agree with you that the game doesn't hold up to the gorgeous 2D offerings of "A Boy and His Blob" and "Wario Land: Shake It!" but I do have to point out that the intent of this "Rebirth" series is to make games that look like they were made for the SNES. It took it's cue from "Mega Man 9."
Perhaps that may help you formulate your opinion of how the game is looking now. I for one love it's retro-ness. I will be purchasing Wii Points for this one for sure.
The graphics and sound both seem incredibly cartoony to me. In my opinion the best thing about Castlevania is the atmosphere, so I'm pretty disapointed.