FO3 had technical issues on modern machines, probably still unsolved. Both games are ugly as sin by today’s standards and most definitely not new PC material. I would be looking at FO4 instead.
That said, not sure why looking to acquire games, each one of which could potentially keep you busy for a long, long time, after admitting to having suitable backlog. If you played The Witcher 2 to completion that would take some 40 hours for one narrative path, maybe somewhat less for your second playthrough. The Witcher 1 doing side quests is probably more than 80 hours to get to the end.
Assuming you don’t serially bounce off all these games, at the very minimum you’re looking to 5-15 hours each, and more realistically 30 to 60, depending on your endurance. It’s not unheard of, people getting up to 80-100 or even more. I have 300 in Skyrim, and I’m an effing butterfly.
1 Just Cause + 1 Metal Gear + 1 Fallout + Skyrim + NMS or Subnautica + Witchers + AssCreeds + Far Cries + GTA + Something else too?? = DOZENS and DOZENS and DOZENS of hours of gameplay that, in real life, could range from MONTHS to YEARS.
Want to buy something that you couldn’t previously play, for the sake of it? Sure, pick one or two. What people think of games in a franchise depends on a lot of things, many of which can be totally irrelevant to you: there is no substitute for getting your hands dirty.
Other than that, there’s a sale every day, these days, anyway, unless looking at something that is out-of-the-ordinary cheap, there’s usually little point in stocking up, some of these games, especially older ones, may even turn up as freebies in this or that store.
PS: the omission of Dark Souls hasn’t gone unnoticed.