Doomed to succeed!
First: I know nothing about Doom.
Having said that, I would like to congratulate you on being the first person to interest me in Doom! Maybe I'll be able to fully enjoy this movie another time after learning what Doom is really about.
In any case, your flash was entertaining, flowed very smoothly, plus your style matched the mood of the parody quite nicely. The sound FX and precise timing of the movie were excellent and were largely responsible for keeping me interested. It's hard for me to watch something when I know I'm not completely understanding it, but you managed to get me to watch it 5 times so that I could write this review for you.
Blasting the wall and then entering through the door was a classic scene that made me chuckle. It was nicely executed. I also enjoyed the scene where Stalvern was growing older. The transitions as he grew were sharp and his expressions were well crafted.
There are two reasons why I rated this an 8 instead of higher:
1) - I had difficulty hearing the narration at various points either because your voice seemed to fade or the music was too loud. After watching it 4 more times I was able to hear the lines I missed, but upon first viewing it, missing narration hampered the story.
2) - You were probably feeling rushed, but I felt that your artwork wasn't as clean towards the end of the flash. You started with really crisp characters and environments but ended it a little sloppy. Maybe it was supposed to look more messy because it was a fight scene and everything was destroyed from the roof collapsing?
Anyway, nice work and thanks for the entertainment!