Huitzil and Pyron's endings from Night Warriors are actually in the first game but mostly go unused since they aren't playable. Hacking the game to play as them and beat the game as them will play their endings but with garbage text reading "AAAAAAAAAAA." They also have alternate player colors if selected with a different button.
Vampire Hunter 2 was made using Vampire Savior's engine, but with the Night Warriors cast. However, the new characters from VS remain as residual data, only their portraits remain except Lilith's, whose sprites and animations are all still present and functional. She can be selected by hacking and the game can be completed just fine if you use her, the only drawback being her lack of voice, victory BGM and that there's a chance the game might pit you against another Dummied Out vs. character in arcade mode.
The creative teams at Capcom want to do a fourth one (Yoshinori Ono in particular is interested in making the project happen), but the suits won't let them, even despite A) the massive fan demand for one, and B) Capcom constantly including the series' characters in crossover games.
This came to a head when Capcom released Darkstalkers Resurrection, effectively the arcade builds of Night Warriors and Vampire Savior with a minor use of HD graphics and no real unlockables. note The other games developed by Iron Galaxy Studios were either games that had never released before in home versions or included several beneficial unlocks. Darkstalkers Resurrection only had a gallery mode.. To say the fandom was pissed when Capcom declared its failure meant a full fourth game release was cancelled is understating it.
The hastily-released Japan-only arcade updatesVampire Savior 2 and Vampire Hunter 2 are widely regarded as having heavily damaged public interest in the series. On top of being slightly modified versions of Vampire Savior (and said modifications being largely disliked), the roster was split between two separate games due to hardware limitations, and the Vampire Hunter 2title was misleading due to the original Vampire Hunter being a fairly different game gameplay-wise. Even the fact that three previously dropped characters were brought back into the mix wasn't enough to counter all the negatives, and series' remaining fans quickly abandoned these versions in favor of previous entries. Every Darkstalkers release since has been some kind of port of the existing entries in the series.
Darkstalkers Resurrection, a decently-featured but still overpriced port of Vampire Hunter and Vampire Savior. It failed to meet its projected sales. Unfortunately, Capcom took that as a sign that interest in the franchise was overestimated, and as a result decided against making a new Darkstalkers game.
The OVA was initially released by Viz Media on VHS and DVD, but those releases are now out of print. Fortunately averted now that Discotek Media has picked up the license.
The American Darkstalkers cartoon, along with the Street Fighter and Mega Man cartoons, was distributed on DVD by ADV Films, before going out of print due to the company going under. Sadly, while the Street Fighter and Mega Man cartoons have been license-rescued by Discotek Media, the Darkstalkers cartoon has yet to be rescued, though Discotek license-rescuing the OVA as noted above has given rise to some hope.
Vampire Hunter 2 (Which features everyone in Vampire Savior sans the characters introduced in that game) and Vampire Savior 2 (Which features everyone in Vampire Savior except Jon Talbain, Rikuo and Sasquatch; plus Pyron, Huitzil and Donovan) never left Japan. We did get Darkstalkers 3 though, which is sort of a mash-up of the two.
There's also Vampire Chronicle for Matching Service for the Dreamcast (though the PlayStation Portable port known as Darkstalkers Chronicle: The Chaos Tower was brought over to the States) and Vampire: Darkstalkers Collection for the PlayStation 2.
Old Shame: Frank Brunner, who did animation for the American cartoon, openly called it "mindless garbage".
Nobuyuki Hiyama voices both Demitri and Pyron. In Night Warriors/Vampire Hunter he gets a third character in the form of Donovan.
Yuji Ueda voices Jon Talbain, Lord Raptor and Rikuo.
Kan Tokumaru voices Anakaris, Bishamon, Sasquatch, and Victor.
In the western cartoon, Scott McNeil voices both Rikuo and Lord Raptor.
Miyuki Matsushita voices both Q-Bee and B.B.Hood in Darkstalkers 3/Vampire Savior.
What Could Have Been: Udon proposed to do an HD remake of the original series, similar to Street Fighter II and even drew up some concept sprites of Morrigan. Capcom turned them down however, citing that, unlike the SFII, Darkstalkers had more animation spites and just saw it as too much work to put into.