1) The Original Frankenstein film is the one of the most important movies in the genre. Every horror movie centered around reanimating the dead owes itself to this classic. Everything about it is just classic. The laboratory sets, the legendary scene for the Monster's birth, the climactic scene in the burning windmill, and the great performances of Colin Clive and of course, Boris Karloff in his break out performance as the monster all combine to make one of my favorite films of the era. James Whales' direction adds an extra layer of class that elevates the film above what it probably would have been otherwise. Also, I do prefer the film over its novel, mainly because of the sympathy I feel for the mute monster, who feels confused and more a victim of his circumstances.
2) And in what was probably the first case in cinema history of the sequel surpassing the original, Bride of Frankenstein turned out to be probably my favorite of the entire Universal line up. Reuniting Whales, Clive, Karloff, and make up genius Jack Pierce and giving them a bigger budget resulted in a film that was way ahead of its time. This includes having a great film score (at a time when full scores were rare), additional special effects, themes and elements that were daring for the time, and the additions of the wonderfully devilish Dr. Pretorious and Elsa Lanchester as the titular and iconic Bride. I love how the movie took one small element of the original book (The Monster's desire for a mate) that was omitted from the 1st film and got an entire movie out of it. Also, the Monster's development here into an even more tragic figure gives the film a surprising amount of heart (the scene with the Blind Man kills me every time I watch it). It is a little disappointing that The Bride never shows up again in the series...oh what could have been.
3) Son of Frankenstein was a return for the franchise after the regime change at Universal, and it turned out to be a great entry. It doesn't quite get the love that the first two films do, but I think it deserves to be ranked right up their with them. The real gold here is with the wonderful cast. I'm a big Sherlock Holmes nut, so its a treat to see Basil Rathbone as the star of a Frankenstein film, and he does a terrific job. I also love Lionel Atwell's fantastic Inspector character, who is charming, admirable, determined, and tragic as well. And anyone who thinks that Lugosi can only do Dracula would be well served to check this out as his turn as Ygor is fantastic, and arguably the best performance of his career. If there is any fault with the film, this is definitely Karloff's weakest turn as The Monster as he's given the least interesting things to do (also that furry vest looks weird, lol), but everything else around him is so great, that its hard to dwell on it. The climax is particularly wild and is worth a look.
4) Ghost of Frankenstein is one where people can point to and call it a decline of the series from high class film making to total B Movie schlock. I can see that argument. Its the weakest film up to this point by far. It has some weird breaks from continuity with the last film, nothing about it seems as grand as the first 3. However, what it lacks in class, it makes up for in sheer insanity. For one thing, this movie puts The Monster on trial. Yup, they chain him up and put him on trial. Its so silly, I can't help but kind of love it. And I won't spoil the ending, but its absolutely insane. Its bound to leave an impression. This is also the first time Karloff did not play the monster, with Lon Cheney Jr. in the role, and he does an admirable job with all the weird material he's given and having such (literal) big shoes to fill, though he never quite has the heart that the original monster had.
5) Frankenstein Meets The Wolfman is historically significant for being the first time that Universal crossed over two of its big monster stars, making it, as far as I know, the first cinematic crossover ever. Everything you see today with the MCU can be trace its roots back to what Universal did with its monsters back in the day, and I think its worth bringing up. The movie is more of a Wolfman sequel than a Frankenstein one as its Lon Cheney Jr. as Lawrence Talbot who largely carries the film. The graveyard scene detailing the return of The Wolfman is fantastic, and one of the best in any of Universal's movies. We also get the return of Maleva the gypsy woman, a key character from the original Wolfman film. With Cheney playing The Wolfman, its Bela Lugosi getting his turn to play The Monster (which actually makes perfect sense given how the last film ended). Sadly, his performance has been mired in controversy given that much of it was reedit and all dialogue removed (despite the fact that Lugosi absolutely played it right given how the last film's conclusion). I'd love to see a version of this film with Lugosi's performance fully intact so I could judge it myself. Controversy aside, the movie is entertaining and just fun. Its fun to have two monsters, its fun to have them interact, and its fun to watch them fight at the end in an explosive climactic battle. Of Universal's crossover movies, its my personal favorite. It lags a little bit in the middle, but it starts strong and ends strong, and its generally entertaining.
6-7) Next up are the big monster mashes: House of Frankenstein and House of Dracula. They are essentially the same movie as they both find fairly convoluted excuses to get The Frankenstein Monster, Dracula, and The Wolfman all in the same movie together. However, in getting them all together, there are some breaks with continuity to make it happen. Also, the movies are a tad messy (HOF in particular feels like its structured like two short films that got spliced together). Narrative issues aside, it is once again colorful and fun to have all these monsters together. House of Frankenstein does give us Karloff in a Mad Scientist role, which is actually neat to have if he isn't going to play The Monster. John Carradine is Dracula and...uh...he's no Lugosi, sorry, but once again, its Lon Cheney Jr who carries the load as he wonderfully plays Lawrence Talbot/The Wolfman. Probably the most satisfying element of these movies is that Talbot kinda gets a happy ending when its all said and done. The Monster in both films is played by the appropriately named Glenn Strange and while he isn't given much in the way of emotional material, he does physically carry the role well and looks imposing. Neither film is a classic, and if I was going to make a list of recommendations or must sees for the Universal Monster films, these films wouldn't get much consideration from me. However, if you're a completest or just want to spend more time with these monsters, then they are fun and colorful looks at them. They both kind of work as like a abridged version of this entire era for Horror films.
8) By the end of the era, the trend had moved the monsters into the realm of comedy by interacting them with the legendary comedy duo of Abbot and Costello for some good ol' spoofs. The first of these films was Abbot and Costello Meets Frankenstein, a weird and wacky crossover of the best that comedy and horror had to offer at the time. Continuity is completely disregarded for this one, so I kind of see it as being separate from the main canon. I also consider this to be the best of the Abbot and Costello Monster films. Not only because it was the first, but because it was the only one where the Monsters themselves were played completely straight. We get Glenn Strange once again playing The Monster, Lon Cheney Jr. once again playing The Wolf Man, and Bela Lugosi (thankfully) returning to play Dracula. And to their credit, they all act as they would in any other monster movie of the time period. What this does is create a great contrast between the monsters and the bumbling antics of their co-stars. To me, its funnier if the Monsters are a legit threat to Abbot and Costello, and it makes for some very fun set pieces. Bud and Lou's reactions are funnier because the Monsters are as terrifying as they'd be in all previous films. If the monsters are a joke (kind of like how The Mummy was treated in that Abbot and Costello film) then it doesn't quite land as well. Also, can you believe that this film is the only time we get Lon Cheney Jr as The Wolf Man and Lugosi as Dracula interacting and even fighting each other? Hard to believe. Now if we could have just gotten Boris Karloff as The Monster again, it would have been the perfect monster party, haha.