I'm not saying you can't enjoy 3/4/76 (okay maybe 76 is pushing it), but they aren't 'really' fallout games.FO3, 4, NV and 76 all add respective elements.
For instance you can ask @Battlegrinder his favorite FO, and it may differ from others.
I like 4 because of the settlement building aspect and the way power armor is done.
The older ones I do like ideas of it, and the more Turn based stuff is nice, but the FPS aspect makes up for it.
Add in the fact you have a massive modding community that can make the old games into FPS.
We have decent mod such as The Frontier for NV, you have New California for NV.
4 has America Rising 2, Sim Settlements 2, FO4 NV, FO4 CW, hell, there is even talk if making 1 and 2 into 4 or NV.
You can't just make an FPS and title it "Halo 6" when it has nothing to do with Halo, and so on.
Also did you just call The Frontier a 'decent mod'? Kek.