I, Monster
1974

You've got to wonder why this film wasn't called Dr Jekyll and Mr Hyde, or some variant thereof. What you' ve basically got is the story, most of the characters, and the setting - but with one huge difference. The main protagonist is called neither Jekyll nor Hyde. Typical.
That said, this is probably the one of the best DJaMH films ever made (top marks have to go to Hammer's far superior - and even dafter - Dr Jekyll And Sister Hyde). For one thing, it's got Christopher Lee and Peter Cushing in it. For another, it's got Mike Raven in it. But let's not hold that against it - even thought the producers give scary Mike the longest speech in the entire film. "Don't cock it up, Mike," they probably said. But cock it up he does.
Lee's kindly but distant doc is experimenting with inhibition relaxing drugs (just the thing for Victorian England - while you're at it, Chris, why not invent the boob tube?) and after giving a dose to the cat proves fatal (for the cat) he does what any self respecting GP would do, he tries it on himself (Harold Shipman take note). This (of course) turns him into a shambling madman. You can tell he's a madman by his messy hair, buck teeth and comedy musical theme.
Of course, eventually the madman takes over, with disastrous results. What makes this film great? Well, the makers ran out of money half way through and had to make do with what they had already filmed (always a sign of quality), and Lee's performance is actually very good - most of the transformation is actually down to his acting skill.
The only downside is Raven's speech, which sees him walking down a street telling us a scene which would have much improved the film had it actually been in it. I suppose the money must have already been running out at this point.
And the other factor that makes it aspire to greatness is that it was apparently filmed in 3D, although no-one seems to randomly chuck stuff at the camera like they usually do in 3D movies. It's also mercifully short.

I, Monster (1974)
Director: Stephen Weeks Writer(s): Robert Louis Stevenson (novel), Milton Subotsky
Cast: Christopher Lee - Dr. Charles Marlowe/Edward Blake, Peter Cushing - Frederick Utterson, Mike Raven - Enfield, Richard Hurndall - Lanyon, George Merritt - Poole, Susan Jameson - Diane Thomas, Kenneth J. Warren - Mr. Deane (as Kenneth Warren), Michael Des Barres - Street Tough, Aimée Delamain - Landlady, Marjie Lawrence - Annie, Ian McCulloch - Man At Bar