Well, this came up in the turn of the policies for tag aliases and implications, so let's go ahead and list out everything. Since I suck at a good formnat, I'll go ahead and put things in alias chains.
*screws it*
OK, for the series, "akumajo_dracula" → "castlevania" seems the preferred.
For the first couple games, there doesn't seem to be enough material or necessity to worry about them for now (the Castlevania Chronicles art prolly being the closest to distinctionary).
For Castlevania III, "castlevania_iii:_dracula's_curse" is most 'consistent', with a "akumajo_densetsu" alias (and possible noncolon alias) added. What I'd like to know is if the simple "castlevania_iii" and/or "castlevania_3" tags should be bothered with, or if perhaps even "dracula's_curse" could be made an alias (this last one not as prominent as the following).
"castlevania:_rondo_of_blood". A non-colon alias, an "akunajo_dracula_x_chi_no_rondo" alias, and, since this is getting into the range of subtitles (c wat i did thar?), I'd suggest "rondo_of_blood", too, as has been done for the FF spinoffs (namely VII's). This enters my question about "dracula_x" and/or "dracula_xx" (the SNES version).
"castlevania:_symphony_of_the_night". Here's where the Romaji-vs-Translated aliases come in, since I understand there's moonspeak in the Japanese titles, but there's also an accepted (if not official) English-text subtitle. Perhaps both should? And, again, the subtitle and non-colon aliases.
"castlevania:_circle_of_the_moon", "castlevania:_harmony_of_dissonance", "castlevania:_aria_of_sorrow", "castlevania:_dawn_of_sorrow", "castlevania:_protrait_of_ruin", and "castlevania:_order_of_ecclesia". The obvious aside, these are especially wonked by the Romaji/English/Localized titles, especially for PoR, since all three show up on the Japanese site.
"castlevania_64" vs "castlevania:_legacy_of_darkness": From what I understand, CV:LoD is basically an expanded CV64. However, the one (one?) CV64 pic features the outfit shown in that first release; I don't know if it is available in LoD, but if not, should there be implication, and if so, should there be aliasing? (Note: The timeline bundled with PoR includes them seperately; not sure what story-based timelines do on the Japanese sites that feature them.)
"castlevania:_lament_of innocence" and "castlevania:_curse_of_darkness": CoD is more straightforward, but LoI is simply "Castlevania" in Japan, so... Not sure what kinda aliaswork, if any, would be applied.
"casltevania:_bloodlines": There is a colon there, right? Anyway, in Japan it's Vampire Killer (should that alias for the Belmonts'/Belmondos' whip, or is it too generic-looking?), and England/Europe(/Australia?) as Castlevania: The New Generation.
Let's see... Should "super_castlevania_iv" alias to whatever'd be used for the first game, and is there anything for "the_castlevania_adventure", "castlevania_ii:_belmont's_revenge", and/or "castlevania_legends"?
Oh, and character names... Aside from the seemingly-accepted "Belmondo" variant, Travor/Ralph of CV3/CoD is a tangle, Soleiyu/Soleil (though there's nothing of him, what I can tell), Carrie Fernandez vs Belnades (Trivia: HoD's instruction manual says the Belmont clan has "blood ties to the Fernandez Family"), whatever Soma Cruz's (sir)name is in Japan (scoured the two sites, but it's all moonspeak), a "wind_(castlevania)" → "eric_lecarde" implication (or alias, but since "arikado_genya" is implicated, "wind" might oughta be), the removal of first-name tags for PoR's vampire sisters (would that constitute being spoilery?)...
That's all that comes to mind for now, and it's all rather rambled, but would this do as the starting post to solidifying Castlevania's tagular presence on Danbooru?
Updated