I actually really like the "Underworld" movies, overall. The whole series has a mountain of problems following it from sequel to sequel, but the whole production is so unblinkingly, unironically wrapped-up in itself that it almost feels like conventional aesthetic criticism doesn't "matter" - like the golden age Bond movies or the "Rocky" series, it more-or-less demands to be met on it's own terms.
Helpfully, other than the first film sucking for almost a FULL HOUR before it suddenly gets interesting and engaging, the terms are pretty reasonable - for a franchise comprised chiefly of complicated-for-complication's-sake revisionist vampire fan-fiction and director/producer Len Wiseman's (largely successful) attempt to enshrine wife Kate Beckinsale as an iconic genre-film sex-goddess; the whole affair has been pretty damn watchable.
For those not up to speed on the "Underworld" lore: Vampires and Werewolves are real - except Werewolves are called "Lycans" - and the two teams don't get along (Lycans = blue-collar, Vamps = aristocrats) on account of the Lycans having once been Vampire slaves until some star-crossed-lovers stuff went down between a wolf-guy and a vamp-princess back in medieval times; and they've been fighting the equivalent of an unseen-by-humanity mob war (hence the title) for centuries. Oh, and they share a common ancestor in some guy who made himself immortal trying to cure a plague and passed the gene on to his twin sons who were bitten by a wolf and bat, respectively.
Beckinsale is Selene, a vampiress with a blackbelt in wolf-exterminating who winds up on the outskirts of the fight after she falls for Scott Speedman as a guy who's been mutated into a vampire/lycan Hybrid and learns that the monster-war backstory is actually MORE complicated than she thought - bad guys who aren't so bad, good guys who're secretly evil, the usual. To it's credit, the franchise keeps track of this information in what was initially a novel way: When "Underworld" vampires drink blood, they also absorb the bleeder's memories.
"Underworld 3" was actually a prequel, with Michael Sheen (really!) and Rhona Mitra as the lycan/vamp Romeo & Juliet analogues. "Awakening" brings back Selene and takes the story to the next logical step: At some point between Part 2 and now, human beings finally found out about vampires and werewolves being real and tried to wipe them out. After a prologue explaining this, Selene wakes up sans-Michael in science lab where we learn she's been locked up for eleven years. The movie makes a big deal out of this "lost decade" business, but it doesn't really have much resonance - part of the "conceit" of the previous films was a near-total lack of reference to where or when ANY of this was actually taking place beyond "medieval times" and "modern big-city."
So, despite the whole "it's the future now" setup, everything is pretty familiar: Selene running about in her black pleather skin-suit and duster beating up enemies, some of whom can morph into big bipedal wolf-monsters. I will say that I like that the series maintains it's creatures-eye-view conception of it's world despite the new wrinkle of actively-involved humanity - it's a trip that our ostensible heroine casually murders human canon-fodder en-route to her various goals since, hey, to her these are basically just free-range cattle, after all.
Granted, it's at last become impossible to ignore that the series really isn't "about" anything other than it's own worldbuilding (it really does have NOTHING to "say" after four films than "here's the next addition to the 'Underworld' mythos!") so at this point it's all about the novelties - this time around, the "new stuff" includes a giant-size mega-Lycan, Stephen Rea(!) as a scientist and a pair of fairly surprising plot twists.
I don't really know that I "needed" a fourth one of these, and I'm not exactly demanding a fifth one... but I can't say it's not worth a shot.