Gaslight (1940), directed by Thorold Dickinson and starring Austrian actor Anton Walbrook and English actor Diana Wynyard, is the first film version of Patrick Hamilton's 1938 play Gas Light. This British version preceded the American film Gaslight, the more famous of the two, which was directed by George Cukor and stars Ingrid Bergman and Charles Boyer, released in 1944.
Watching the two Gaslight films back to back, it's impossible not to compare them. The one with Ingrid Bergman is better because it's a smoother-told story, and we get to know the characters at a deeper level as well as their relationships, plus the sets are richer and contribute more to the narrative. Its predecessor, however, does have its share of memorable scenes, such as the cancan dance towards the end, and the bits with the dog. There wasn't a dog in the American version, probably because they realized the presence of a dog makes the victim appear less isolated. In the British version, Bella Mallen (Wynyard) also gets outside more than her counterpart in the American film, and although she's manipulated in the same ways (often exactly the same), she's not as closed in as Bergman's character.
As for Anton Walbrook vs. Charles Boyer, I'd say they're about even on the evil and devious scales. Boyer's character comes across as more calculating, whereas Walbrook is creepily zany. I didn't think I'd like the 1940 adaptation as much as I did; it was well worth watching to see how the films were different and for it's singularities.