#1 - Fallout 1 is the GOAT - It has the tightest narrative, the greatest antagonist in the series, and is really only marred by the whole "time limit" aspects.
#2 - FO: Tactics - Without a doubt the best tactical combat in the classic Fallout engine. Large squad sizes, positioning matters more, suppression and overlapping FoFs, massively improved weapon variety, etc. Real-time with pause was surprisingly done pretty well, you got to outfit/equip a "squad" rather than just some lone wanderer, vehicles being a large feature (even despite the bugs) finally, all the cool Brotherhood of Steel stuff where you're receiving missions from command, advancing through the ranks, etc. It often got straight to the point without all the need for heavy travelling, dialogue, quest chains, etc. Sure, it was a fairly mediocre "RPG", but it's a fucking fantastic tactical squad game and the only one that is featured in the series.
#3 - FO: 2 - Probably could've taken my #1 spot if it wasn't for all the goddamn pop culture bullshit. Plus, there's the fact that the game was very rushed - meaning it had a ton of weird bugs, jank, etc. (which I'm willing to forgive them for considering the year it released - but still tarnishes the game a bit).
The rest aren't worth discussing. FO does not belong in the FPS genre and should've been called something else. They are all the fakest and gayest titles in the series. We can argue about which ones are faker and which ones are gayer, but nonetheless, they are all some variation of fake and gay.