Basically, I want the following in order of priority:
1. Cooperative multiplayer. Let 2-4 players share that great experience.
2. Better mechanics: No level scaling, traits added, expanded and elaborate hacking, advanced stealth, more perks, realistic combat (skills shouldn't impact damage - that's what the weapons themselves are for - and make combat LETHAL, where every single bullet counts), and the option to play "hardcore" style - beyond FO:NV. Make scavenging into something you REALLY need to do - to survive. Don't let the first couple of hours be enough to live happily ever after - and make everything scarce where it makes sense, and don't have a ton of stuff lying around where bandits have roamed a million times before, as in: reward people for finding hidden stuff.
3. Fewer locations but with a lot more depth and detail. I want the world to feel more handcrafted and interconnected, instead of being an open landscape with a lot of "cool" places. I want to find old vaults full of lore, personal logs, and just more stuff to explore/figure out - rather than just killing things.
4. Better writing and a compelling main narrative. Don't go Obsidian with pretentious try-hard-to-be-serious stuff and don't stick with Bethesda over-the-top zany crap. Also, don't go Hollywood melodrama like Bioware. Look towards games like Last of Us or Bioshock Infinite for how to write compelling stuff.
5. New technology - as the Gamebryo/Creation engine is getting really quaint. Take advantage of PC hardware - and implement TRUE streaming, rather than dividing something like Vegas into a zillion cell segments. At the very least, make all major locations be single cell areas.
6. C&C with a significant impact on the world - and with a good mixture of both grey area decisions and clear-cut decisions. Don't spell out the consequences, but let them dawn on the player through dynamic chances in the game world.
