I love using Outfit Studio to mesh things together and make new outfits. So in short the thing that keeps me coming back is the Aesthetics of the world and the ability to mod it with new weapons clothing etc...
I'm a huge sucker for modded outfits. That's why I use outfit studio and am currently learning how to use Blender for my own little projects

For me, The gameplay that's about it. I LOVEE the game-play but everything else like the settlement building and the role playing aspect just turns me away from the game and that's what makes a Fallout game for me really wishes they played it more like a traditional fallout game on a Role-playing stand point and take notes on what NV did right and add on to that, but that's a whole other topic.

I come back to Fallout 4 if there are interesting mods released for it particularly weapon or clothing mods which are my favorite.

The hope that one day we'll get a mod like Resurrection or Regrowth that doesnt need Far Harbour *cough* Hint *Cough*

Right now ? Nothing, and that will probably not change anytime soon. I feel like there's nothing inteteresting about it, which I haven't seen after my playthrough, the game just feels soulless to me. I might come back in a year or never, gonna stick with FNV.

Frost mod recently released. I ain't gunna be done with Fallout 4 for a while now.

I really like the locations in this game. The main story leaves something to be desired but I find myself itching to get another playthrough in, so that's what I'm about to do. I'll explore mostly, ignore the main questline for as long as I can, then finish it up sometime later.

Anything post apoc related and I'm there lol. As per fallout 4, honestly I don't think id play it if it wasn't for the mods out there to better improve the game. The story could of been a little more interesting and in depth. Ive made so many characters and always find something new to find in the game.