Let's start by ruling out every character who is in the armed forces / a PMC / any lifestyle where they deliberately put themselves in the line of fire [of bullets]. These people consider being shot at a part of the job. Being shot at more sucks, but it logically sucks even more if you aren't meant to be shot at at all!
So, Gordon Freeman, the Vault 101 resident, Abe, etc. all have a much suckier time than Master Chief, Marcus Fenix, Nathan Hale, etc.
Next, we consider how well-equipped the person is to deal with a bad situation.
-Gordon Freeman is a fucking genius. He also has a HEV that acts pretty much as Power Armour. No official weapons training though.
-101's skills vary based on the life choices you make, but realistically the guy / gal has spent his/her entire life locked up underground. Weapons training consists of shooting a BB gun at targets / roaches, and playing baseball. Oh, and I guess beating up kids at school if you go the evil route. Armour consists of whatever you can steal, and even that wears out after a few hits.
-Abe has the ability to possess people, but otherwise he's useless. Possessing is frickin' awesome though.
Generally speaking, we should at this point remove anyone with supernatural powers from the equation; being mortal sucks far more than being Superman, regardless of how your day is.
From here it gets tricky... I mean, using the examples I've given, how do you decide which sucks more? Aliens invading (intact) modern America, or surviving in America after the Chinese (or possibly other Americans) have nuked every square inch of it?
I don't have an answer to this question... but hopefully my post will help people evaluate their own answers.