Parody.
I think people judging this too harshly don't see it's a parody. Kinda like Braindead/Dead alive.
It could have been done better but if you can't tell the humour you're lost.
I love "Split Second", it's a guilty pleasure of mine, but sadly I don't think there's much humour beyond the Duke Nukem-ish one-liners. They wanted to make a "Blade Runner meets Predator meets Alien meets serial killer" deal, but they ended up with a half-assed effort.
I remember reading that the script was originally supposed to be a buddy-cop movie ('a la Lethal Weapon) about ritual killings in LA. It then ended up in the hands of these Brit producers who decided to turn it into a Sci-Fi\Horror set in a then-futuristic London - and you can tell this new version was pretty hastily written.