I played 3, 4 and New Vegas, and F3 is for me easy best Fallout game that I played, great atmosphere and great pacing.

Every Fallout game after 2 shouldn’t be allowed to be called Fallout.

I loved Fallout 1 to death, but I voted 2 here because it was the same as 1 but with more content (even if the freshness of 1 was gone when 2 rolled out).

I haven't played any other Fallout games, only New Vegas 

They are fully turned-based, not real-time with optional pauses on different triggers like BGs. If you like classic CRPGs with lot of role playing options, do try them, arguably nothing beats them at that till this very day (especially FO2).

That's most likely true - even NV, made by some of original crew, can't hold the candle to first 2 games. As for Bethesda...well, they at least tried with FO3, it's just they don't know how to make better game than reskinned TES and were pretty much completely oblivious of what makes first 2 Fallouts great. Of course, let's not talk about FO4 at all, that's not even RPG to start with, let alone Fallout.

Even better, I love turn-based games. Obviously if it is used, meaning I have many options to choose from and the options are all meaningful. Fallout sounds like it.

Fallout 2 or Fallout New Vegas

Fallout 2 is easily my favorite. While the original had a bit more freedom it had a lot of issues that I think 2 ironed out. You just can't beat old school CRPG writing/mechanics.

No prob! I hope you enjoy it a lot like I did.

Probably new vegas. I got caught in the hype of fallout 4, and it's not till you are done and sit and think about to realize how much petty time was wasted. Maybe it's the idea of getting somewhere exciting or the story getting somewhere that keeps you playing, or the the cheap habib of looting and collecting all these items, which don't lead anywhere significant, and the similarity of the side missions. The game is a great time waster/filler, but i can't think of moments of greatness, besides that terminator enemy. And the hours spent on building almost every camp, and defending.... The dlc's werent that good either. Fallout 5 better be a great evolution, in terms of story,  graphics, AI, physics, enemy types and the way they attack and respond/behave. But i doubt it. It will be a reskin on top of the old formula and same gameplay.

Gotta say I never liked fallout. Tried playing New vegas and fallout 3 but I think the game's just not for me. Never enjoyed 1st person RPG's adn honestly hated how buggy it felt. Same thing about most of Elder scrolls.