I think it is fairly safe to say that if you did not like any of the other installments in the Underworld movie series then you will not like this one.
As usual with these kind of movies it is one where you preferably switch of most higher brain functions before watching and just sit down and enjoy the show. The movie is certainly not a masterpiece when it comes to story and script. Actually the script is, at times, fairly crappy. There are for example a sequence were the Lycans are attacking the stronghold castle of the Vampires and the script writer taught it was a good idea to just let them drive straight into the center of the castle and breach the door before they got challenged. What the f…?
On the whole the script is a typical Hollywood B-movie concoction that holds little merit. If this would have been the first movie in the series I think there would never had been a series made at all.
So why did I like it then? Well, even if the script is nothing to write home about it is not a total disaster and it serves as an excuse to provide 90 minutes of good entertaining Vampire vs Lycan action. Plain and simple.
Of course Kate Beckinsale is a good reason for liking the movie as well. Her moving around in her intimidating (and good looking) skintight clothes slashing up Lycans in various creative ways makes up for some of the not so stellar script. I probably pissed of a bunch of feminists there but it is not really like a care about that.
The action and the CGI is reasonably well done and another reason to like the movie. Actually, come to think about it, Kate Beckinsale, the action and the CGI is pretty much the reasons I liked this movie.
They could have selected a more charismatic bad guy though. For most of the movie I felt Marcus was bland and even a bit dull.
It is not the best movie in the series but it does not exactly shame the series either. For me, I have to rate my enjoyment of it as above average compared to movies in general.