you want a first person sandbox "fuck it all" kind of game that doesn't necessarily give you superpowers.
I can't deliver on the first person, or COMPLETELY void you of being a superhuman, but I'll do my best. Anyways, here's a list of what kinda comes to mind
Crackdown 1 - Right before getting into monsters, the game is essentially GTA had you been the hulk in a skin-tight outfit.
Crackdown 2 - Same as the first except with more stuff. Less humans though :<
Just Cause 1 - This is everything that you want except in a tropical setting, and no first person. Can't have everything.
Just Cause 2 - The same except you're on even more roids.
Serious Sam series - Quick and funny, shoot weird things in humorous adrenaline horror. It's arcade-y and not very open to interaction besides shooting things, but it's fun.
Dishonored - Not entirely sandboxy, and not in the setting you want, but I believe it follows everything else to the letter.
Farcry 3 - The same issues as Just Cause except, what's this, you're in first person now!
Hitman Series - There isn't free-roaming, but you can get the kicks from most levels. Very entertaining exploration. You're not very powerful without stealth however.
APB Reloaded - This one is an MMO. A free one at that. Imagine GTA online with a few issues but much more customization.
If you're not liking the titles I bought up, let me know with a few more details. Admittedly, the world isn't filled with first person sandboxes.