For those who may have not seen the movies in these two series (and why not?), I'll say this in brief: The Underworld movies are about a centuries-long war between vampires (who are very aristocratic) and the "Lycans" (werewolves) who used to be their slaves. There's a Romeo and Juliet angle, and some plot elements which seem to have been borrowed by the Twilight books (based on what Wikipedia tells me).
The Resident Evil movies are based on the popular video game series, and they portray a world gradually taken over by zombies.
Both series are centered around strong female warrior characters: Selene (Kate Beckinsale) in the Underworld movies, and Alice (Milla Jovovich) in the Resident Evil movies. Both series have now gone to four movies, with the most recent one in 3D, and the fifth Resident Evil movie is coming in September.
Here are the lessons I've learned by comparing the two series:
1) A series shouldn't be a series of the same thing over and over.
I just saw the current Underworld movie recently, and it had advantages over some of the predecessors (better direction in the action sequences, for example), but it was clearly More of the Same. You liked the earlier ones? Well, here's some more. We might refer to this as Iron Man Syndrome (AKA "don't rock the boat"). Even the look of the movie is the same, that nearly black and white (or black and dark blue) color palette that has been there since the first movie.
The new movie is set in the U.S. for the first time, but everything still looks the same, and also the change is less striking than it might be because it was never clear where the earlier films were taking place anyway. There's less romance and more ass-kicking than in the first two movies (the third was a prequel, not featuring Selene, and so it sort of sits by itself), but it's still just a continuation.
The Resident Evil films have each been quite different. The first was almost all underground, very claustrophobic. The second was in a city, over the course of one night; the third was in a desert and mostly in bright sunlight; and the most recent was in a variety of settings. Throughout the series, the zombies have become less and less of a plot element as the series has transformed into an action-adventure story. So, not just more of the same.
2) Who am I rooting for again?
With the Underworld movies, sometimes it seems we're rooting for the vampires (because the main character in three of the movies is a vampire), though the vampires are pretty rotten to the Lycans and their entire power structure is based on lies. In the third movie, about the slave rebellion where the Lycans freed themselves, we're clearly rooting for the Lycans, but with the new movie we're back with Selene. It seems that ultimately we're rooting for whoever is the star of the movie.
From the beginning of the most recent movie Selene kicks mucho ass, including killing a lot of people (she isn't called a Death Dealer for nothing), but, aside from the badassery of some of the fights, I did start to wonder if all the people getting killed actually deserved it. The whole thing works better if you don't think about it very much (even apart from the fact that the plot of the most recent movie was very confusing – at least until I figured out that they were using the same plot as the movie Ultraviolet, which made it much easier to follow 🙂 ).
With Resident Evil, it's much clearer. The Umbrella Corporation (a huge multinational corporation specializing in consumer products, medicine, viral weapons, and general nastiness) are evil. They (admittedly somewhat accidentally) wiped out most of humanity, and are still experimenting with the same viral weapons that turned most of the world into a zombie disaster area. So, they're evil. Alice (and whatever few survivors are grouped around her in each movie) are generally good, though not uniformly. As for Alice herself, she's my answer when people complain (with reason) that all the current superhero movies are so boy-oriented. Where are the female superheroes? Well, here's one. She doesn't wear a cape and she doesn't have a letter on her chest, but otherwise she fits all the criteria.
3) Challenge your protagonist.
As I say, the action in the most recent Underworld movie was the best so far, but at this point Selene is so powerful (and so pissed off, and now even immune to sunlight) that there's not much tension in the fights. The Lycans she's fighting get bigger and bigger, but you know she'll kick their big shaggy asses sooner or later.
The smartest thing the Resident Evil people did with the most recent movie was de-power Alice right at the beginning. She was originally one of the Umbrella Corporation's bio-weapons, with all sorts of special powers, but this also made her increasingly difficult to challenge. So, Umbrella "took back its property" and left her as an extremely capable soldier. This was, as I say, a really good idea.
This applies more generally. In mysteries, for example, the reader loses interest if the detective is never stumped.
4) Remember the Bechdel Test.
In some ways the most striking difference between the series is that the Underworld movies are basically "Selene and the boys." There are no other strong female characters, and (as far as I can remember) movies #2 and #3 have no significant female characters at all other than the leads.
(By the way, one of the weird thing about these movies is that we never see any female werewolves at all. And nobody ever mentions it. At least the Lord of the Rings movies mentioned the Entwives and the apparent lack of female dwarves.)
The Resident Evil films always have a variety of female characters: scientists, soldiers, a TV reporter, a student, a doctor, a nurse, an actress, a cop, and a girl named Kmart. The women in these movies have many conversations, about many subjects other than men. One of my favorite scenes in Resident Evil: Apocalypse is on a deserted street, in a disabled bus, where three women basically analyze their desperate situation and their limited options, each one bringing different expertise to bear, while the only male character protests in vain that things aren't really as bad as they actually are.
This is not a scene you're going to see in the upcoming Avengers movie, or the last X-Men movie, or pretty much any other mainstream superhero movie that I'm aware of.