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Doubts that Witcher 3 can beat FO4. FO4 feels... whole. Witcher 3, while incredible in a lot of ways, loses in some areas to FO4. Are they areas they'll use to judge GOTY? Maybe not. They're pretty niche, but stuck out badly to me. Here's an example:
Open World: Witcher 3 vs FO4 - Right now FO4 is winning big time for me. Witcher 3 spoon fed me tons of icons right on my map. I knew where to go, all the time. It was never really so much "exploring" as it was just running to certain waypoints I knew about for specific things. FO4 is exciting and terrifying in it's exploration. They don't hold your hand, you legitimately explore in every sense of the word and you discover areas stuffed with loot that reward said exploration. It's just the best you can ask for. FO4 definitely wins there.
Story? Witcher 3 is winning here, no contest. I mean, Witcher 3 felt like playing a movie. Every side quest was genuinely interesting and captivating. A lot of FO4 side quests are by-the-numbers, but some do have intriguing twists and turns. But, quest for quest, Witcher 3 wins for sure.
Characters and writing? Again, Witcher 3 by a landslide so far. I genuinely felt at home when surrounded by certain characters in that game, and truly cared about their outcomes. Some of my ... poorer decisions that let to some of their fates legitimately made me both upset and regretful. It was a really weird, but satisfying and rewarding way to play a game. FO4... well, some characters are okay, but these people I'm dealing with don't compare to Yen or Tris or Lambert etc, it's not close. Witcher 3 wins here, no contest.
Combat - I think FO4 wins here. Witcher 3, towards the end, was very boring from a combat perspective. You realize that you really don't have many moves, and you mostly go through the same routine in every. Single. Fight. Cast shield, use buffs, swing swing igni, re-cast shield, rinse repeat, chop chop everything's dead. Snooze. Even Death March was a joke. The story was so good that this didn't ruin the game, but FO4's combat is INSANE. It's so fun. the VATS system, and the AI of the enemies, and the varied weapons, plus companions, and Power Armor, or big enemies like Death Claws jumping up out of the ground, I mean the list goes on... and I feel like I'm trying new things and treating each fight like it's own based on the terrain around me and other factors, etc. FO4 has had a more rewarding combat gameplay experience for me thus far.
Itemization - Again, Witcher 3 failed me here. I HATED it's loot system. It was incredibly boring, very easy to abuse and once I had my not-so-hard-to-make baller set, I literally never changed armor. There was never a need to, nothing came close. Itemization from loot was super sloppy - if I killed an enemy ten levels ahead of me, I still looted loot exactly tied to my level. Snooze. If I risk something crazy, getting a great reward is the best feeling. FO4 loot is off the chain. Legendary enemies, when found, are really exciting because if you die, they're gone. They're random spawns. Random enemies come and go; it won't be there when you get up. It's do or die. The crafting, and the discovery of items around houses and in chests, and the varied combat based on the weapons you're using, is great. FO4 wins, easy.
I could go on but these points really show the divide I'm unsure about. Witcher 3 was an incredible game with an awesome story and characters, but a lackluster combat system and poor itemization. Fallout 4 is also an incredible game with an awesome combat system, great loot itemization, but medium-quality character dialogue and more by the numbers questing.
So which game wins in the eyes of GOTY? The problem I see is that a game can have a mediocre story/characters, but if the gameplay is top notch I usually can overlook it because I'm having a blast PLAYING it. If the gameplay lets me down, sure the story can keep me on the edge of my seat and I'll love playing it, but as soon as I'm done with the story I usually put it down and walk right away. With FO4... I could see myself doing EVERYTHING this game has to offer, and continuing to just play it for fun to progress and build on my settlements and exploring, well after the main story is done. I had no interest in doing that with Witcher after a while. I just shrugged and went to the next game, even loving it as much as I did. I felt "done" after beating the story.