Frankenstein is, without a doubt, one of the greatest horror films of all time. It is also one of the greatest films period. What director James Whale did with this film is nothing short of perfection. As you watch it, notice the angles and forced perspectives of the graveyard, the tower and the final chase scenes. There is hardly a perpendicular line to be found anywhere. Furthermore, the stage backdrops with their dark backlit clouds set an ominous tone that enhances the film greatly. In contrast to these scenes the "normal" places are shot on location and everything is neat and clean: The town, the lake, Baron Frankenstein's mansion. Amazing cinematography for 1931 or any year for that matter.
Boris Karloff's Monster is sheer perfection. The make-up is flawlessand his ability to make that heavy costume come to life is astonishing. In the documentary that accompanies the film they said that Karloff suffered back problems because of the sheer weight of the Monster's costume. When he was on break he had to sit in a special reclining chair in order to get some relief. Colin Clive is perfect as Henry Frankenstein. He embodies his character with touches of brilliance, ego and insanity all rolled up into one. Edward Van Sloan as Dr. Waldman also gives a knockout performance [Is it just me or does he provide the inspiration for the Criminologist in Rocky Horror Picture Show?] as does Dr. Frankenstein's side kick, Dwight Frye as Fritz [not Egor!!!].
I've seen every remake and incarnation of Frankenstein and none of them can light a candle to the original. It has inspired countless filmmakers and fans alike. If you've never seen it, put this one on the top of your list. Furthermore, if you're a fan of Frankenstein and you've never seen Bill Condon's Gods and Monsters (1998) I consider it to be a fitting tribute to one of the greatest directors of all time. I don't believe that Frankenstein is available to view legally online for free, but you can watch it instantly on Netflix. If you know differently, let me know. I own Frankenstein: The Legacy Collection which includes not only the original film but the four sequels that followed. It's well worth the purchase price. Personally, to see this film online with poor resolution is a crime. See it on the best screen possible.
For more info check out the film's entry in IMDB.