Personally, some of the items said here I could deal with. Fallout would be hell but a hell that is livable in. Demon's Souls would suck like all hell but then again you are immortal for as long as you have that Nexus binding and after getting out you would be a demi-god. Halo would also suck but then again you'll likely know more about military combat then the marines and if you don't go to boot-camp and learn the easy way.
Dead Space would be a major one for me as unless you've memorized everything or have a detailed map with you, you will either (1 Walk into a safe room (2 Come face to face with a 'morph or (3 enter a room with either no gravity or oxygen). Silent Hill would also be bad as you'd probably piss your self after encountering one creature.
Now, for the first items, if you weren't in a good enough position to get/find any weapons/magic/armor/The Jesus Christ of their universe then yes they would be hell and you would die horribly, painfully, maybe a bit strangely. I still think I could make it in those realities
