Favourite definately Fallout, not that it's perfect or even close but it is well written nicely balanced and fun. Not too big that it requires a lot of combat filler, the really obvious pop culture references are kept to the special encounters that you might not even find. And the retro futuristic theme is subtle, just enough to lift the game above being generic post apocalyptic fodder without going over board with hundreds of energy weapons and power armour equipped troops running around. Plus it nicely explains the presence of energy weapons, robots and power armour.
Fallout Tactics comes a close second for me, the lovechild of Fallout and Jagged Alliance. Or so was promised, but had neither the roleplaying of the former or tactical options of the latter. Instead it was the redheaded stepchild with Fallout's limited combat and Jagged Alliance's minimal roleplaying, oops someone got those the wrong way round.
But in it's way FOT was far closer to Wasteland, and personally I think it's still got the best combat out of all the Fallout games Fallout 3 and New Vegas included.
Probably Fallout Tactics greatest sin was it's art design which was more anime than retro futuristic but after playing Fallout New Vegas I've come to realise that I'm more of a fan of Fallout's mechanics rather than the retro futurism.
Fallout New Vegas a distant third. The combat sucks, I laugh at those claims that first person is so more immersive. Nothing is more immersion breaking for me than to see three to four shots hit between and opponents eyes and they still keep on coming. First person, even third person and hit points/skill point damage do not go together. The story is tight though, sure New Vegas itself is pretty much a rehash of New Reno but it's easy to ignore for most of the game. I do like the survival aspects, I wish I could mod these into Tactics.
Fallout 2 is where the rot really set in pure quantity over quality and comes last for me (not played FBOS or Fallout 3). The Enclave, if they had to have a remnant of the prewar government/military that had access to high tech equipment why didn't they just use the Brotherhood? Sure the Brotherhood were isolationist and more concerned with preserving technology than what was going on in the Wasteland but exposure to the Vault Dweller and the threat of the Master's army could of changed all that. It would of added a nice twist to the game especially if you'd enlisted their help in Fallout. It would of most certainly put a stop to the Brotherhood as noble knights righting wrongs in the wasteland. They had the NCR Rangers for that. Plus with the Brotherhood as the bad guys while it's not far fetched to see them get involved in the outside world there is no way they would have traded away energy weapons to New Reno. Then there would also be no need to invent new more powerful power armour, two things that just add to the power creep.
New Reno, while it might be well written and offer great role playing decisions like KotOR 2's main plot it just doesn't fit the setting. Probably the 50's clothing in the vault of the future artwork confused them and led to Thirties style mobsters? Perhaps if the artwork in Fallout had shown people dressed like the Jetsons instead this might have been avoided? Likewise if Gizmo's hadn't of had working slot machines and used the gaming tables for mutant roach fights or some other strange made up games for people to bet on, then New Reno and New Vegas might of turned out to be rather different towns.
Talking Deathclaws, which led to hairy talking Deathclaws, or Mutant Death Goats as I like to call them, in Tactics. In Fallout Deathclaws are mysterious and rare and powerful. There's a great sense of foreboding built before you meet one. Then you meet one and it sees you and then you are reloading, and then reloading and then maybe if you're really lucky you get a lucky critical and you think I never want to meet one again. Then you walk around the corner and... But in Fallout 2 the main deathclaws are intelligent, and while not exactly cuddly you get to recruit one and then in Tactics you get to recruit loads. Now in New Vegas they are quite bad arse again but they do seem to be everywhere.
The real World Guns, sure the P90 and G11 are just stupid additions, but most of the rest of the real guns make some sense. Grease guns would be a logical weapon for the Gun Runners to manufacture, revolvers a much better option for use with reloads using homemade propellants. If only they'd added to all the descriptions a Gun Runners manufacturing mark. Most of the real world guns in Fallout are easter egg references but all non energy weapons (except miniguns and perhaps rocket launchers) should have been explicitly depicted as being produced post war by either the Gun Runners or the Brotherhood. There should have been a clearer delineation between pre and post war produced tech and the intro movie could have shown the soldier in the execution scene using a plasma or laser pistol instead of the 10mm. Perhaps the Gun Runners did produce most of the normal weapons, my memory is a little hazy but they also sold some energy weapons leading to the impression that they were also producing energy weapons. Which in my opinion started the power creep in the following games. Instead it just opened the doors for developers to add any gun that took their fancy to the series.
The great Vault experiment, in Fallout vaults were just shelters, they knew there was a strong possibility of war and prepared for it. In Fallout 2 they were suddenly part of some social experiment why? It adds nothing to the setting except opportunity for the developers to get really wacky. Is it really logical that with war looming they would go to the expense of building these vaults for some experiment when survival would be a much more imminent concern? Sure there wouldn't be enough vaults for everyone, but that didn't stop governments in the real world (during the cold war) from building their own such shelters. The most illogical part was the experiment didn't start until the bombs dropped, shouldn't they have been experimenting before people had to go in them for real? If they didn't know how people would cope how could they determine someone was going to be around to view the results?
A much better idea would have been to have the player discover a test vault populated by the descendants (or their corpses) of volunteers who had gone in prewar to see if the vaults were a viable survival option. The test subjects were meant to have been let out eventually but then the bombs came and the experiments turned into reality. The developers would have been able to explore the same ideas but without having every future game needing a weird and wonderful experimental purpose for any vaults. And the Pop culture references, has any game ever before or since contained so many pop culture references? What is this a post nuclear role playing game or an easter egg hunt?
Then there's the Tribals, now I have no problem with the idea of groups regressing so much in so short a time, read Lord of the Flies or Earth Abides. But Fallout already had low tech tribals, the Khans and people of Shady Sands for instance, was there really a need to add half naked primitives to the setting?