I've come to realize that this one is the best, especially after the last patch.
Now my argument isn't entirely fair because I only played Fallout 1, Fallout 3 and F:NV. But I understand that Tactics wasn't that great and FO2 was kind of goofy.
F:NV is the best because it has the most to offer all things considered. FO1 was great, really one of PC game's classics, and probably had the best post apocalyptic "feel". However, that game had no where near the scope of quests, weapons, and of course graphics. Fallout 3 was more of an action game than a legitimate RPG - I had so much fun in FO3, but most of my time in that game was just killing things and all my characters ended up almost exactly the same.
In FO:NV you really get the best of all worlds. I really "feel" like I'm playing a character of my choosing. Killing is secondary to dealing with people, which makes it much more RPGish and realistic. F:NV has an inter-connected world of characters; what you do in one place may change how things work in another. You must make decisions that will negatively affect one person or faction while postitively affecting another person or faction. Stealth also helps if you don't want to work with people, there are many quests that allow you a "stealhty" route - want to find some dirt on someone? just sneak in and find their dirty secrets.
You build the world your in. You forge alliances, you make friends and enemies, you decide who is good and bad from your perspective. You decide who gets to run new vegas, but that choice isn't always easy.
The weapon selection is MASSIVE, a host of guns, melee weapons, cool energy weapons, mods, etc.
F:NV does extremely well to capture a 1950s -> post nuclear, out west feel. This was a slow burner for me... Once you start trekking around, listening to the music, talking to the people you get a definate "cowboy world after nukes feel" - at first it seems cheesy but then it starts to really fit with fallout world/real world.
The problem with F:NV is that it's not an instant classic like FO1, and it doesn't have the "wow effect" of Fo3 (picking through the ruins of washington DC was amazing)
F:NV is a slow burner. Once you play through it a couple of times and really start to realize how well done the character scape is and how accurate the atmosphere really is + all the other goodies it really is an amazing game.
The one thing that sets F:NV apart from oh-so-many other RPGs is the character scape (as I like to call it). Too many RPGs are just "pick this way to kill". This is something better, you have so many options to deal with characters. Fighting is an important but secondary feature, and I think it's why it hasn't received as much attention as other fallouts as well as other RPGs.
This is the lead factor in making it the best because when it comes to a post-nuclear world because it's interesting to think what people would live in that world - F:NV offers this better than the others in the series IMO. Among all the other things mentioned.
