Here are some random thoughts...
Lots has been said about original Dracula with Bela Lugosi, and the Spanish version with Carlos Villarías, so I needn't comment here. Dracula's Daughter (1936) is an interesting take, with the daughter of the title trying to find a cure for her need for blood. Not a great film, but at least not a carbon copy retread, either.
Son of Dracula (1943) is also different, and really stood out in a number of ways. First is that we get to see, thanks to some quick animation, Drac turn into a bat. Pretty rough but still would have wowed them in the day. What wowed me was the smoke effects, as Dracula and his new girlie assume vapour form a number of times. While often rough, it was much more effective than I would have thought possible.
Son of Dracula also had a wonderful oh-fuck! moment, one that I don't think I've seen used in another Dracula film... or anywhere at all. It was cool because it made sense. Drac knew about two possible threats and instead of faffing about, took action immediately.
Sadly, Lon Chaney Jr. isn't a great Dracula. But it is a good little film, and an interesting sequel.
Bride of Frankenstein (1935) was better than I remembered. It has some awful comedy shoe-horned into it, but if you ignore that, it's quite a reasonable film. Karloff is marvelous again in the part of the creature, and his last moments are quite sad.
Son of Frankenstein (1939) is an amazing watch with an all-star main cast - Boris Karloff, Basil Rathbone, Bela Lugosi, and Lionel Atwill - and a good script by Willis Cooper. Just bloody great watching four good actors ply their trade.
Ghost of Frankenstein (1942) is another interesting sequel. Bela Lugosi's Ygor is back, as villainous as ever. Sadly, Lon Chaney Jr. is pretty ordinary as the monster, except for at the very end, when he puts in a chilling performance. Interestingly, it's also at the end of this film where we get the classic Frankenstein's monster walk - arms stretched out in front, stiff legged and slow - which is picked up by the following film, Frankenstein Meets the Wolf Man (1943).
Before I talk about that, let me pause and say that Lon Chaney Jr. may not have been a great Dracula or Frankenstein's monster, but he absolutely kicks arse as the Wolf Man. In the first film, The Wolf Man (1941), he has some scenes that make him, as Lawrence Talbot, into a very creepy stalker-type - hey, they had different ideas of what was charming and cheeky back then! But it's once the curse takes over and he starts to transform that his performance steps up a notch. It's not as the Wolf Man that Lon Chaney Jr. shines, it's as Lawrence Talbot, the happy go lucky playboy type who gradually becomes the man desperate to find a way to stop himself from hurting people. Though Wolf Man is not his best performance in this role.
In Frankenstein Meets the Wolf Man Talbot's horrified to find himself alive once more. Realising he's effectively immortal, all he wants to do is die, to end his own life so that he won't hurt others. He's just so ernest in his wish for death, you can't help but feel sorry for him. It's a great performance.
Interestingly, it's in this film that Bela Lugosi finally plays Frankenstein's monster, the part he had rejected many years before. Sadly, he's not very good. Actually he may have been quite good, but they edited the scenes that had the monster talking, and any reference to its affliction from the previous film. And the ending is sadly obvious, not to mention sudden.
There's a definite continuity running through the films, with the occasional minor tweak to help with an aspect of whichever film you're watching. The only real continuity problem is the Frankenstein monster's on-again, off-again ability to speak. Though this can be explained away by some of the things that happen to the creature through the films, if you can be bothered caring enough to need to.
It amazes me the directions they took these films. They were never content with just retreading the previous ones, they actually tried to continue the stories and characters. Okay, the Frankenstein ones tend towards creature-needs-fixing, find-another-Frankenstein-to-do-it, but they still manage some variety.
Frankenstein Meets the Wolf Man is particularly interesting to me, because Frankenstein's monster doesn't even appear for the first half hour - it's a film about Lawrence Talbot - the monster is merely a possible means to an end.
Son of Dracula also goes off in odd directions, plot-wise. I rather like the intelligence of the characters in it at times, one spotting that Count Alucard is Dracula spelt backwards pretty much straight away. Nice to have someone spot obvious clue immediately.
House of Frankenstein (1944) is another ensemble piece featuring Dracula, the Wolf Man, and the Frankenstein monster. It's a schizoid little piece, giving us a brand new mad scientist, well played by Karloff, and a new hunchbacked assistant who ends up part of a bizarre love triangle with a gypsy girl and the Wolf Man. While not great, it's better than it sounds, though it does feel like Dracula was thrown in as a afterthought.
House of Dracula (1945) is the last of the run and another ensemble piece. Dracula, Frankenstein's monster, the Wolf Man, a mad scientist, and yes, yet another hunchbacked helper, plus a run of outlandish coincidences. The weakest of this bunch of films, it is noteworthy for finishing the Wolf Man story arc.
House of Dracula was originally called The Wolf Man vs. Dracula but that script was rejected by the Hays Office as being too violent. Interestingly, it featured the Wolf Man fighting Dracula in the form of a giant bat at the finale - shades of Van Helsing.
All up, I enjoyed going through these films. The quality is sometimes variable, but it was interesting viewing nonetheless. Now I've started working through the Hammer Horrors - will be interesting to see how they hold up.