Karloff went on to reprise his role as the monster (never mind that the movie ends with the monster's death) in Bride of Frankenstein, Son of Frankenstein, and House of Frankenstein, and was the Mummy in The Mummy.
You can always impress your friends if they never knew that Terry Jean Bollette is now better known as Hulk Hogan or that Boris Karloff was once known only as William Henry Pratt.
Mary Shelley's Frankenstein has been brought to the stage and screen in numerous incarnations, most notably in the 1931 film starring Boris Karloff as the monster.
The image that people associate with the name "Frankenstein" is the one created by/for Boris Karloff as the monster.
Boris Karloff is credited in the opening credits as '?', presumably to preserve an air of mystery before hand.