Frankenstein and Bride of Frankenstein; Boris Karloff in Frankenstein 1970; Gene Wilder in Young Frankensein; Raul Julia in Frankenstein Unbound.
Son of Frankenstein. This is an obvious choice, but the truth is that there just aren't many great performances as the monster; most movies present the creature as an inarticulate brute, which doesn't offer actors much to work with. Karloff did a lot to establish that precedent, but even his grunting, lumbering creation has some soul, especially compared to the actors who took over for him in the later Universal movies. For better or worse, this is the version of Frankenstein's monster that will forever be remembered. Honorable mentions: Michael Gwynn in The Revenge of Frankenstein; Michael Sarrazin in Frankenstein: The True Story; Clancy Brown in The Bride.
Frankenhooker; Helena Bonham Carter in Mary Shelley's Frankenstein.
Best line: You would think that "It's alive!" would win this hands down, but I have to go with Flesh for Frankenstein's immortal "To know death, Otto, you have to fuck life ... in the gall bladder!"