The video is said to be from a game called Warhammer 40,000: Space Marine which is set in the Warhammer universe and plays basically like every shooter you've seen since Doom was launched. The nine and a half minutes of the video show a Space Marine which manages to take out a host of Chaos spawn.
The commentator seems to be a developer on the game, a guy that explains why the team has chosen to make combat “up-close, personal, visceral melee experience” while also saying that “we have range combat in the game, and it's fun and important, but properly used, it's really a means to end in order to get up close to the enemy, where the player has a tactical advantage. We call this intimate brutality”. Anyone that uses the concept “intimate brutality” must be a Warhammer developer as far as I am concerned.
The Internet rumor mill suggests that this game, which is set to launch when the under the radar Warhammer 40,000 MMO launches, is in development for the PC, the PlayStation 3 and the Xbox 360 and the clip is probably showing the Xbox 360 version of the game in action.
THQ has said nothing related to such a game and has refused, so far, to comment on the leaked video.
We might be facing a very elaborate hoax but, unless THQ comes out and says that this is a video from a canceled project, I will believe that a Warhammer 40,000 shooter is in development and I'll spend a whole lot of time thinking about the ways in which this game could be great.
The gameplay featured in this video is nothing like Doom or any shooter like Doom. It's more akin to Gears of War or even Tomb Raider. It's third person, with a dynamic camera, rather than the fixed "throguh the characters eyes" view common to Doom clones.
Just thought I'd correct you on that horrendously wrong sweeping statement.