Well, it seems you don't get what I'm saying. I said that the two (FO1&2 and FO3) were not the same and therefor always will have two different fan bases considering different versions of the game to be the "true" Fallout, and as long as Bethesda franchises the new fallout games as a continuation of the old we will always have this debate. Because of this, IMO, Fallout 3 might be considered the definite Fallout game by some, and not by others. And that was my answer to the OP.
I'm not talking about sales smash here (besides, picking a number like 50k without anything to compare with, what does that say?).
I'm talking about how it was recieved by the general gaming community and how much it was talked about.
You have some good points, but your overall message is incorrect I believe. My opinion on all of this is pretty simple. Nobody, no matter who you are, can rightfully claim something as the definitive title if you didn't experience all of them. Period. Same with movies. You can't be a movie critic and claim a particular movie of a series is 'the definitive title' if you've never even seen the others. I would say that just because some 90% of people might think of the 3rd one as the definitive title doesn't make it so, because it's only an uninformed opinion, considering they likely never played the originals, let alone heard of them. Take for example the above poster who's friend commented about the game's name, case in point. Being ignorant and uninformed of the history of the series pretty much means you have little influence among those that do, as you've probably seen on the boards.
However, I still do agree that likely 99% of the people who played FO3 as their first one would consider it definitive. But I would disagree, as would most people who've had the honor of experiencing the originals.
I would like to point out that I myself have only played the originals just starting a couple months ago, for the first time. I ordered them from a great site called GOG.com and you can actually get downloadable copies of the original 2 (plus Tactics) for only $6 a piece. Not to mention all their titles are DRM free, patched to the latest official version, and include everything you need in an easy to download .exe installer. /shameless plug