This is a video created by MetalBallStudios comparing the size of various famous video game monsters (previously: size comparisons of Star Trek ships, various sci-fi franchise ships, movie robots and movie monsters). Although I would hardly call Sackboy or Ratchet or Daxter and a couple of the others monsters. Also, the video's creator admits that he accidentally made the Deathclaw from the Fallout franchise 6-meters (20-feet) tall instead of the 3-meters (10-feet) it should have been. It happens. I know first-hand when you see one for the first time they certainly seems twenty feet tall. Terrifying, really. It's kind of like when-- "It's nothing like when your doctor tells you to drop your pants." You don't know that! I had to pay for a new examination table AND patch the wall.
Keep going for the video.
Thanks to Dave W, who agrees the biggest video game monster of all time is the person playing who would purposefully kill all their lemmings.