I couldn't recommend Dishonored more; the level design is really open-ended, and there are always multiple different ways to accomplish a goal. The DLC is fantastic, too, if you find yourself a fan of the base game.

Really, the main thing Bethesda needs to do to step up their stealth game is incorporate more stealth aspects into Radiant AI. It's already really easy for them to program both specific patrols and general sandbox movement, and Radiant AI is pretty much all about responding to and using their surroundings. If an enemy sees the corpse of a friend, or detects us and then loses track of us, they go into alert mode; if they're in alert mode and detect an alarm mechanism, they'll go and activate it. If they detect one of their allies is in alert mode, they'll go into alert mode themselves and possibly spout some alert dialog.

There are some other amenities that would improve the stealth (and general) gameplay, too, like letting us sneak under tables or through narrow passages. Leaning from cover could be good for both stealth and FPS gameplay. If Bethesda could include some form of Detect Life appropriately into Fallout, that would be handy too; thermal vision, maybe? If the enemy markers on the compass are like in Skyrim, they'll only appear during combat.

I don't know. I found that some enemies in 3 were sometimes just unrealistically perceptive. It wasn't uncommon for some enemies to detect my silent and unmoving PC through a solid concrete wall one floor down.

I'm really looking forward to the rerelease later this year, also Dishonored 2 looks like it might be good!

People must play a different FO3 than me, I guess.

Enemies are far too sensitive in my game, including using superhuman abilities to psychically know exactly where you are, telepathically communicate with each other, coordinate attacks even though they are brainless ghouls, animals, drug-addicted raiders, etc.

"Better enemy detection" ... sure, okay, except that it has to be realistic reactions, not ridiculous inappropriate reactions that various enemies simply would not and could not have.

There is no fun whatsoever in trying to play a stealthy/ranged character when you get one kill (if you hit) in a party of 10-12 enemies (or even 5-6) but then the entire group in the area (as well as other areas, sometimes) converge on your exact position with superhuman speed and turn the encounter into a boring melee slugfest.

Yeah that's odd. I can literally shoot a raiders head off from stealth and non of the other Raiders react at all. I shot one from the little alleyway in the Fairfax ruins and failed to one hit them and they ran all the way around the buildings to the place where I shot them from. Of course I had displaced by then and killed them as soon as I was hidden again!

Yeah, there are some odd bits in the FO3 stealth system. Like, a missed shot will make noise where it hits, whereas a successful "silent" sneak attack hit is just that - silent. Even though it's pretty obvious that a bullet hit that dude in the face.

And apparently, http://fallout.wikia.com/wiki/Sneak_%28skill%29#Sneak_states.