Locations that are interesting and rewarding to explore, instead of just being filled with debris, generic enemies, and generic loot.

Everything I want has already been stated.

Perks and S.P.E.C.I.A.L. are essential though. I was so upset that Attributes were taken out of Skyrim. They weren't perfect in Oblivion, but I was so upset that they were taken out instead of improved on. Personally, I think the Special stats in FO3 were much better than the Attributes with it's limited way of raising them. Even then, getting multiple high SPECIAL stats felt like an accomplishment.

Depth is also another thing. As long as has, at least, the same Depth as Fallout 3, I'll be happy. More is welcome.

I think what I'm saying is, don't gut the game.

EDIT: Aiming down the sights as well. Might get some flak, but Fallout 3 feels awkward with it's aiming system.

Terminal hacking redone to essentially match the skill as it exists in Vampire:Bloodlines.

The terminals have actual passwords, that can be guessed; or found; but the hacking skill; (quite unrealistically) gives the appearance of working it out, and entering the correct password ~if the skill is high enough.

- Better Character creation

- Factions work more like factions in nv

- Able to unlock doors with explosives

- Romance your companions (same-six romances too)

- Thirst/Hunger/Sleep needs

- More energy weapons

A reputation system: So my actions are remembered an thus have consequences.

Multiple Options for every quest with multiple outcomes, main quest being very important.

For it to not be so clear cut "Good vs Evil" but make it so every faction in the game has good and bad things about them to various degrees. Even the fiends in Fallout New Vegas were drug addicts and there are characters that felt sympathy for them.

A hardcoe Mode.

No more annoying Children.

Low Intelligence Dialogue.

I am sure there's more but that is what comes to mind right off the bat.