Just a few notes concerning Fallout 4...
I'm definitely not saying that Fallout 4 won't be good / fun at release. In fact, I do genuinely believe that of all Bethesda games so far Fallout 4 might well end up being the most stable and polished vanilla (at release) title that they've made. Now, with this said, just like any Bethesda games before, Fallout 4 is guaranteed to have numerous bugs and [most likely] instability issues nonetheless (given the size and complexity of their games' world, it's a given).
A few things are 100% certain with Bethesda games to consider:
1) Mods that fix aspects / features of their game. And I'm not talking about "patches", but actual mods that were needed, taking the famous Skyrim GUI mod(s) (of course a popular one being SkyUI) as an example, ones that were necessary if you wanted an actual PC-friendly GUI out of the game. And something that Bethesda themselves never did internally on their own (still can't fathom why) and merely let the community do it (that's probably why they never did it themselves, too).
2) Unofficial community patch(es) that fix a nearly impossible-to-count number of bugs and various other issues (from misplaced doors to improperly-layered textures or scripts that don't trigger when they should to missing sounds, etc). Now, it is true that many fixes from such community patches aren't exactly details that A) you ever saw yourself in any of your sessions, or B) you didn't even know existed to start with and never seemed to affect your games in any way, shape and form.
Additionally, some fixes aren't technical 'fixes' per se but mere "changes" that are a source of disagreements (if anything). But I want to stress (and speaking from experience) that such community patches' accumulated fixes amount for more good than "bad" in the end. If I take both Oblivion and Skyrim as examples I can safely say that after installing their respective unofficial patches my saved games stopped being corrupted and my long-term play sessions were given a God's blessing to remain stable with virtually no crashes (when otherwise it would crash on a regular basis, at least once every 30 minutes, sometimes less).
I'm talking about unofficial patches because, obviously, Fallout 4 won't have it at release. I for one will be waiting for it (at least for that, if not for more from actual mods) before taking the plunge.
3) DLCs. It's of course quite early to talk about Fallout 4 add-ons, but we all know they're inevitable. If anything, I wouldn't pre-order nor would I buy Fallout 4 on release day if I wouldn't be aware ahead of time of what's to come (if they do announce any of the DLCs prior to the game's actual release, obviously) and how much it'd cost me if I was to buy any of said DLCs. Not to mention that it's possible that Bethesda throws some kind of a "Season Pass" special offer at us (that would honestly not surprise me at all, seems to be a trend in gaming since the past few years).
Now, don't get me wrong...
I loved Morrowind, Oblivion, Fallout 3 (although I myself modded more for that one than I actually played... quite a mistake in retrospect) and Skyrim very much so, all of them pretty much equally (despite my issues with them all especially initially soon after release, with crashes and other general instability issues).
But, here's the thing, Bethesda games always need at least a full year after release before they truly shine and show their potential (if said potential is finally being exploited to a good extent after that much time, if anything). So, with all of that in mind, and from my own experience with their games, I'm inclined to not even consider Fallout 4 as a 2015 candidate for GOTY to start with, but would rather reserve that honor for 2016 (I know... it's technically a 2015 game, but it's a Bethesda game, too... think about that for a moment).