Of course it justifies it. Game Development is a business, not a dreamland. Thats a reality that some people seem to reject to accept.
I don't think it justifies it. You cannot blanket justify all things in the pursuit of the dollar; doesn't mean that you can't get away with it legally, but it does not justify it.
10 years passed between F2 and F3. Many old gamers retired and many new gamers don't know about old Fallouts. And today's market depends on today's gamers, not the ones from the past decade. Bethesda took a place where they wouldn't need to trouble themselves with breaking lore (I think you would be more angry if they choose to place the game into west coast) and tried to use many old factions (especially BoS and Enclave) to introduce new players to the world of Fallout. That brought nostalgia in old players and made entrance to new fans easier.
This is true, but this also means that Bethesda did not have to spend 6? million dollars to buy the Fallout name so they could make a post apocalyptic RPG; their intended market has mostly never heard of it, and thinks Fallout 3 is the first game; and New Vegas the second. They could have called it "Outlands" or "Wasteworld" or whatever they wished, and the bulk of the consumers wouldn't care either way. Calling it "Fallout 3" only ticks off those that expected a proper Fallout 3 derived from Fallout 1& 2 instead of TES. Had it not been called Fallout 3, I'd have bought it without baggage along with everyone else that bought it without even the slightest foreknowledge of it being a series. :shrug:
It gained practically nothing from it, it only made use of the mascot and a couple of names. A company could write a game that breaks no canon in a series [any series], and imply that its the same world, but in a different location and with different technology and characters living in a different century, and it would be scarcely different than was done with Fallout 3. :shrug:
**In fact... Interplay did just that with Fallout 1 ~but they didn't call it Wasteland 2, and it certainly wasn't a sequel.
Though it was very familiar....
http://i271.photobucket.com/albums/jj125/Gizmojunk/example2.jpg
http://i271.photobucket.com/albums/jj125/Gizmojunk/example1.jpg
At the same time, Bethesda has its own style of making RPG's and their own fanbase (TES fanbase... which could be attracted into Fallout fanbase as well). F3 gameplay is more similar to TES gameplay for both of those reasons. Some old Fallout fans may cry and scream because of that, but many of us are content with that so your argument only stands for some of old fans and a minority of the current Fallout fanbase. Enough elements from the old Fallouts stay for this to still be called Fallout.
That is the problem. They make one game, over and over. Its a good game and they try to improve it each time, but its opposite spectrum from the Fallout series ~they just dressed up TES with a new setting and cosmetic relabeling. There are no significant differences to either game... save dismemberment. They are almost as alike as Doom and Heretic.
One cannot play Fallout in Fallout 3, for the same reason one cannot play Warcraft 3 in World of Warcraft. (notice WoW is not called Warcraft 4)
The argument you state doesn't seem to hold true for Blizzard, as they clearly understand the term sequel, and Starcraft 2 and Diablo 2 and 3 are what one would expect from sequels to those series.