I think it partly depends on what appeals to you more.
For roleplaying, 1 and 2 are probably the best but of course the UI and appearance are far worse than the others.
For building, 4 is clearly the best especially if you use building mods. Above all, Place Everywhere. That mod alone utterly transforms building. Add in mods to effectively remove the building budget, mods to increase the allowed settlement height and/or radius, mods to increase what can be scrapped, mods to change the terrain, mods to add thousands of extra buildable items, mods to change textures of buildable items, mods to allow you to blueprint buildings or sections of buildings so you can duplicate them easily...you can turn FO4 into a genuinely good building game, where you really are rebuilding society. Scavving missions to acquire materials, building to make new settlements. You can even install a variety of related mods to have the settlers do the building under your management to a chooseable degree (the Sim Settlements mods). The story, however, is poop. I played for ~200 hours before I finished it and did it only to get it out of the way. I didn't care at all.
For story, I think NV is best. I didn't finish 3 because of the escort mission near the end, but I did enjoy exploring and reading the background stories. Also, 3 has an unappealing start. The entire opening section is effectively just a tutorial - the game itself doesn't really start until you leave the vault. It would be easy to be put off by the frankly rather dull start.
Mods change everything (and is one of the many reasons why FO76 is rather bad). For example, the full dialogue mod is arguably essential if you want to play FO4 as anything other than a mediocre FPS. It certainly adds a lot to the game.
I think I have a bias towards 4 because it's the only one I've played with mods. Mods are a really big deal.
For roleplaying, 1 and 2 are probably the best but of course the UI and appearance are far worse than the others.
For building, 4 is clearly the best especially if you use building mods. Above all, Place Everywhere. That mod alone utterly transforms building. Add in mods to effectively remove the building budget, mods to increase the allowed settlement height and/or radius, mods to increase what can be scrapped, mods to change the terrain, mods to add thousands of extra buildable items, mods to change textures of buildable items, mods to allow you to blueprint buildings or sections of buildings so you can duplicate them easily...you can turn FO4 into a genuinely good building game, where you really are rebuilding society. Scavving missions to acquire materials, building to make new settlements. You can even install a variety of related mods to have the settlers do the building under your management to a chooseable degree (the Sim Settlements mods). The story, however, is poop. I played for ~200 hours before I finished it and did it only to get it out of the way. I didn't care at all.
For story, I think NV is best. I didn't finish 3 because of the escort mission near the end, but I did enjoy exploring and reading the background stories. Also, 3 has an unappealing start. The entire opening section is effectively just a tutorial - the game itself doesn't really start until you leave the vault. It would be easy to be put off by the frankly rather dull start.
Mods change everything (and is one of the many reasons why FO76 is rather bad). For example, the full dialogue mod is arguably essential if you want to play FO4 as anything other than a mediocre FPS. It certainly adds a lot to the game.
I think I have a bias towards 4 because it's the only one I've played with mods. Mods are a really big deal.