More of a puzzle game than a shooter
Everyone likes to criticize the voice acting and story, and so they do not pay any attention to them. So then they play the game and get pwnt. Why? Because your teammates tell you explicitly to not engage the Nightwalkers; stealth is emphasized over action. This game is not like Blade where the vampires can be killed en masse with silver nitrate rounds (Although the pistol fires silver bullets, but they have almost no effect). In Vampire Rain, your weapons are nearly powerless and so you have to use stealth.
Everyone likes to say the game is a rip-off of Splinter Cell and MGS. But in a game where you are a government commando sent in with advanced technology to infiltrate and kill things, THIS is likely how you are going to look, and so it shares a similarity with other stealth-action government commando style games. Let's look at other genres for instance:
In WW2 games each one of them has Tommy Guns and M1 Garand rifles; does that mean they are all rip-offs of Medal of Honor?
In Saints Row you play as a criminal who steals cars and kills policeman so is it a GTA rip-off?
In the end the game can be enjoyable if you approach it with an objective mind. It does have some faults, such as the graphics, music, and the fact that it makes you repeat a lot of the same things, but none of them are enough to sink this game down to the level that it is often placed. I recommend playing the game yourself instead of conforming to the opinions that the majority of reviewers share.
I give this game a 7.5\10