Because it was made by the same people who made The Mummy (Returns) so obviously some mystical creature like vampires should have huge gaping jaws even though they just need to bite your neck. You didn't know that? For shame!
But yes...the movie was stupid, predictable and basically like they took a ton of stories including the Mummy and then copy and pasted.
-Hugh Jackman was a very poor choice for this sort of movie, the mysterious dude not knowing the past thing works when he's Wolverine, in this he really couldn't pull it off.
-Igor was basically Benny from the Mummy with a hump.
-Frankenstein's Monster was more like from the end of Son of Frankenstein.
-The Wolf"man" (seriously...what was the point of including werewolves?) looked like a hairy turd.
-The CG was overdone and a HUGE portion wasn't needed.
-The "lightbomb" was not only ridiculously added, but when it went off it made light come out of EVERY window after being detonated inside a cramped room.
-Van Helsing's "crossbow" was just...stupid. (Glad he wasn't afraid to spray & pray in the middle of a village)
-Dr. Jekyll and Mr. Hyde in here was just as lame in LXG (why on earth are people using the Hulk so much to represent Hyde?) but at least he had a dark side.
Only real pro: Yes this is a real spoiler people, if you're sensitive to them NO TOUCHY!
Wolferine fortunately killed Kate Beckinsale so if a movie was made it would be very difficult for it to be carried by her hype.
Seriously..this is the best way I can explain this as to how this crew has advanced (using the term lightly..):
The Mummy - Batman '89
......................... - Batman Returns
The Mummy Returns - Batman Forever
Scorpian King & Van Helsing - Batman and Robin
If I had to gather a list of movies they ripped...
X-Men
Underworld
Son of Frankenstein
Dead and Loving it
The Mummy
Blade II
I heard that this was based off of a Van Helsing comic book and that's where the whole not remembering the past came from, but somehow I doubt they weren't ripping off Wolverine in the first place.