(or "The Score Stands At 4-1")
If you were to look at a single common thread that ties together the storytelling engines of the Universal horror movies, it would probably be that none of them were ever intended to be continuing series. Watching the end of 'The Wolf Man', you could be forgiven for thinking that a sequel would be utterly impossible--the movie ends with Larry Talbot being bludgeoned to death with a silver-handled cane, the exact same fate he deals out to the werewolf that bit him to begin with. (It's hard to feel a whole lot for Larry, who's a bit too slimy to really be sympathetic, but the stricken look on the face of Claude Rains when he realizes that the beast he killed is his son speaks volumes.)
And yet, legendary writer Curt Siodmak was pressed into the unenviable task of turning this one-off film into a series. Oh, and would it be too much trouble to work the Frankenstein Monster (and later, Dracula) in as well? (Thankfully, he wasn't also given the task of figuring out a way to fit Abbott and Costello in there too.)
There's really only one direction you can go from the end of 'The Wolf Man', and it's to Siodmak's immeasurable credit that he doesn't shy away from it in order to placate delicate sensibilities. If your lead character died at the end of the last movie, and yet is alive at the start of this movie, well, then he has to be immortal. (The opening sequence of 'Frankenstein Meets the Wolf Man', where grave robbers crack open Talbot's tomb to find his perfectly-preserved body, is a classic.) And if you're immortal, and you also happen to turn into a vicious killing machine three nights a month, well...you're going to wish you could die. For those of you who think that entertainment in the 40s was more genteel and wholesome, picture watching five movies about a guy whose fondest wish is suicide. Because the alternative is mass murder.
The problem with this as a storytelling engine is that it's a classic "false status quo". No matter whether he's wishing for death (as in 'Frankenstein Meets the Wolf Man') or a cure (as in 'House of Frankenstein' or 'House of Dracula'), he's doomed to never get what he wants, because if he did there'd be no more Wolf Man to make movies about. He gets his longed-for death four times (by silver, flood, silver, and a plunge into icy waters) and a cure once (via an exotic fungus that makes his skull soft and squishy like Play-Doh so that scientists can mold it into a shape that won't squish his brain, because pressure on the brain is what turns people into werewolves...look, the later Universal movies don't make a whole lot of sense, all right?) But none of it ever takes.
This is actually pretty common in "werewolf" series, but most of them give themselves a little leeway by finding ways to make the bestial side just sympathetic enough that the transformation isn't an unalloyed curse. But again, Siodmak's uncompromising take on the werewolf mythos (while working excellently for a single story) is a little hard on a series. His Wolf Man is pure sadistic killer. All you can do with such a beast is...well, all right, you can lock him up during the full moon to keep him away from random innocent people, but Talbot's kind of a "big picture" guy, OK? He's a bit busy trying to die to worry about the little details.
Later writers (such as Harlan Ellison, Neil Gaiman and Roger Zelazny) have used the Talbot character in one way or another in their stories. Usually, they've adapted the character slightly to the needs of a workable storytelling engine, as well as to their own personal tastes; the post-movie Talbot seems to have grown past his need for death, and accepted his curse of occasionally-hirsute immortality as an opportunity to battle other supernatural monsters. This tiny change turns a difficult-but-workable storytelling engine into a compelling one, and it'd be very interesting to see what could be done with such an idea on the big screen once again.
Oh, come on. A high-budget open-ended series of new "Wolf Man" movies, masterminded by Neil Gaiman and Harlan Ellison--I can dream, can't I?