I think the best performance in that one was Bela Lugosi as Igor. Nailed it. I mean drove it home excellent.
Although he played many parts over the years in the Universal movies, this was the best character for Lionel Atwill as Inspector Krogh. The fake arm and the darts...classic.
So many situations from this movie made it into Mel Brooks Young Frankenstein and it's freakin hilarious.
IMO the best Frankenstein movie..ever..is Bride of Frankenstein. But Son of Frankenstein is absolutely choice vintage.