IDK man, it just seems like Alucard has been more relevant and prominent throughout the years. Granted we're talking about two different eras of Castlevania. Ideally I'd like Alucard and a Belmont. But if it came between the two, I'd say Alucard. He alone has been as prominent as the Belmont Clan for awhile
He's prominent, but nowhere near as prominent and important compared to the entire Belmont clan. Even in the games where a main member doesn't appear, you always have someone related or connected to the Belmonts in the games. Despite the Belmonts not appearing in Bloodlines, Portrait of Ruin, Order of Ecclesia, Castlevania 64 or Circle of the Moon, the playable characters are related to them through blood. The Belmont Clan is connected to Dracula and throughout the entire series, there's always one Belmont or relative around when Dracula is around.
Heck, the reason Symphony of the Night happened and Alucard awoke to deal with the situation was because Richter was missing when Dracula's Castle came back. In all the other games that aren't the Sorrow games or Castlevania 3, Alucard did nothing cause he wasn't needed, except in one case, where he's the one who gave a special Spear to Eric Lecarde. Even in the games where it was the relatives fighting, Alucard did not help them.
Alucard's importance comes from saving Richter Belmont and from his game's popularity influencing the series and introducing Metrovania, but when it comes to the whole series, the Belmonts are much more important because of their influence throughout all of the games.
-In Lament of Innocence, the vow of the Belmonts was made, to hunt the night and their signature weapon, the Vampire Killer is born.
-In Castlevania 3, they were feared and exiled and when Dracula came back, they had to find Trevor in order to defeat him.
-In Symphony of the Night, Alucard awoke because the last known Belmont was missing when Dracula awoke.
-Non-Belmonts had to do a ritual in order to wield the Vampire Killer. This ritual involved the non-Belmont to fight against the Spirit of the Whip, who took the form of Richter Belmont.
-The events of Order of Ecclesia happened because Albus stopped Shanoa's ritual and he saw the opportunity of using the last descendants of the Belmont Clan in order to counteract Dominus' death curse and stop Shanoa from killing herself. And in order to get the True Ending, you needed to rescue all of the Villagers, all of whom are the Belmont's descendants.
-In order to defeat Dracula for good, the Belmont Clan had to leave the fighting to their relatives until 1999, which would allow Julius Belmont to defeat Dracula for good.
For Alucard:
-Castlevania 3
-Bloodlines(referenced)
-Castlevania SotN
-Castlevania Resurrection
-Aria of Sorrow
-Dawn of Sorrow
-Portrait of Ruin(referenced)
-Judgement
-Harmony of Despair
-Lords of Shadow
-Lords of Shadow 2
-Mirror of Fate
They're pretty close. If you don't include Bloodlines and Portrait of Ruin, they're tied. Also didn't include small spin offs like Encore of the Night..
He was in the other 2 Shadow games, but he was never, ever, in the first Lords of Shadow game. Sure, there was that one trailer that featured Alucard, but we know where that went. Also, why are you including a cancelled game? Or did you mean, Castlevania The Adventure with Sonia Belmont? The game that was declared non-canon?