You could claim that all games are really just the same as each other ... but with swapping things about ... Baulders Gate, Planescape Torment, Neverwinter Nights ... all the same. Though there comes a point when so much has to be swapped, that really all you have done is swapped one game for a different game. It's true that Planescape is more in line with Oblivion than Fallout 3 is even remotely in line with Oblivion.
Not after you've played enough games...
Those three in particular are also rather supposed to be very similar; They each are ISO-style RPG's using the same rule sets, and are crafted for players that seek out D&D based cRPG's. :shrug:
(Can you say the same of Fallout and Fallout 3?)
If one thing only has to swapped in a game to be the same as another, then the case for same-ness holds true. If any or much more is different that needs to be swapped, then the case progressively fails to hold true, ending as really being completely different games. When claiming that Fallout 3 is Oblivion with a swap or two, the argument fails because there are just too many differences that need to swapped ... too many differences that make them really different games and game-play.
Well lets see...
Oblivion and FO3 both start you off in a cage; A man comes along and lets you out; You spend the next ? an hour doing a contrived tutorial to learn the basics of play (which amount to stealing and fighting). Suddenly you are attacked, and must flee to the outside through a big round gate, but the game stops you first and asks you if you'd like to recant any or all of your past commitments, then starts you outside on a hill, just a short walk from town... It goes on quite a bit you know... (Both games send you on a manhunt of crucial importance to the fate of the land...)
The topic is Planescape-like game. Planescape starts you off dead
; but no... a Planescape-like game need not even be set in the Planescape worlds; It just needs to be responsive, and have a PC affected dialog tree with deep roots and long branches (that eventually bear fruit).
A TES style game set in the Planescape universe could be really neat, but could not be Planescape 2.
Differences that totally and utterly alter the tactical and strategic needs in game-play, as in the case of Oblivion v Fallout 3...
Such as swords/bows-and-arrows V guns ... utterly different tactical/strategic game-play.
Such as magic V no magic ... utterly different tactical/strategic game-play.
Such as alchemy V no alchemy ... utterly different tactical/strategic game-play.
Such as teleport gates to other worldly planes ... utterly different tactical/strategic game-play.
These are some of the differences that are just too much between Oblivion and Fallout 3, to allow the claim of being the same game but for a swap or two. Too many differences needed in game-play.
How exactly again?
What's the difference between a mace and a nail board? The difference between a rocket and Fireball? The difference between Potions and Drugs (or stims!)? These are the same games and they play i-d-e-n-t-i-c-a-l-l-y below the cosmetic changes.
** And Teleport Gates and Other World Portal have no tactical/or strategic affect unless you can use them against an enemy in a battle...Which you can't in these games (but you could in Baldur's Gate
).
The content (wheels) of both games are so different ...
... and the wheels finally fall off your Oblivion v Fallout 3 argument.
Content is moot; Its the activity of the game that matters. Bethesda would never make a Planescape-Like game, though I can see them making a Planescape setting game, and it being one I might like ~Unless they name it Torment 2, Rise of the Nameless Wanderer.
Planescape ... that now that is much, much more closer to Oblivion.
I don't see it, unless you reduce it to "Special person, goes on a special quest". Remember... In Planescape the PC can level up over lunch. Gameplay between PS:T and any TES game to date is quite dissimilar in both obvious and subtle ways. Both are good, but both are inextricably different.