There's a difference between taking a sip here and there, and having a feast.
Alucard licks his blade and takes a small sip from pretty women now and then- the bare minimum to stay alive.
Dracula drains people dry and eats their hearts.
Alucard has qualms about being the same monster as his father,
Dracula has embraced his monstrous side.
Alucard has also discarded his former identity in all ways, as he can never go back, simply declaring himself his father's antethesis.
Dracula still holds on to "Gabriel", and how he was wronged by everyone, and it's really the whole reason for everything he does. I mean, even his appearance. He's literally Gabriel as he would look a few years shut away in isolation. longer hair, and his beard has grown out.
No matter how much he declares Gabriel Belmont is dead, or he is NO LONGER GABRIEL, WOMAN! I AM THE DRAGON, RAWR! He really still is. Which is why he's so damn eaisly swayed by visions of his wife, and of the son he never saw grow up.
I thought that would be obvious.
Also, Alucard does look prettier than he did in MoF. In MoF his face was much more sullen and gaunt. In LoS2 his face is fuller and prettier looking. So while he hasn't fed enough to have the same level of power as his father, (he still needs a physical weapons as opposed to Gabe who can just manifest his weapons out of pure hate, loneliness and his own blood) or to regain his black hair and some skin tone, he's fed enough to get by, with the side effects being him regaining just enough to not look like a corpse.
once could argue it's a matter of in game graphics not matching art, but Simon and Trevor look just fine, as does Dracula. So it's obviously intentional.
Trevorcard isn't even near the same level of power as his old man, GDrac's powers stem from his battle with the Forgotten One. He absorbed it's vast powers used to tear the opening between realms back to earth before the demon reclimed said power and then cut it down right after. GDrac's powers displayed (the Void Sword, Chaos Claws, Shadow Whip, etc...) are a mixture of his vampiric nature/powers (through Laura's/Carmilla's blood), the unlimited power of the Forgotten One and his own emotions/feelings and other means.
Trevorcard built his powers his own way, evolving to adapt (consuming blood of certain beings, Resurrected Daemon Lord, the Reaver= Demonic Wings and Shadow Claws) collecting broken weapon pieces (the stake attachment to the Vampire Killer, the remains of the Glaciem Rapier and Igneas Greatsword) to forge into his personal sword (the Crissaegrim) and other means.