Ah, gotcha. I was gonna add Legend of the 7 Golden Vampires, but that was a different Van Helsing as well. He did play the same guy in all Frankenstein films, though.Although he played a man named Van Helsing in several movies...it wasn't always the same one....he played relatives of the original in a couple of movies.
On the subject of horror movies, Lon Chaney, Jr. was the Wolf Man 5 times:
THE WOLF MAN
FRANKENSTEIN MEETS THE WOLF MAN
HOUSE OF FRANKENSTEIN
HOUSE OF DRACULA
ABBOTT AND COSTELLO MEET FRANKENSTEIN
And he was The Mummy 3 times:
THE MUMMY'S TOMB
THE MUMMY'S GHOST
THE MUMMY'S CURSE