Why Square Enix forgot to release the final fantasy franchise for the xbox Nintendo answered.
What about
Final Fantasy XI (MMO)? They released it on the Xbox 360.
Square specifically addressed that one game's reason for no ports. It skipped
the original Xbox because of the smaller 8GB HDD, and
the Wii because of its reliance on friends code (that said the GC had some online games without any problem and Capcom had Monster Hunter 3 using their own servers after that).
It seems whatever problems Square had with
Nintendo for an MMO were solved by the time Dragon Quest X came, since that used its own external 16GB storage for the Wii and had a lot of online features coded
by Nintendo on an OS level specifically for DQX. But on the other hand,
Microsoft lost Final Fantasy XIV because they became
less flexible with Square and insisted on no crossplatform online multiplayer.
Microsoft tried to have their replacements for the Final Fantasy games made (Blue Dragon, Lost Odyessy), and to buy temporary exclusivity for Star Ocean 4 and the Last Remnant. Just like most third-party JRPGs part of the
Microsoft timed 360 exclusivity, that had disastrous results for their sales (even killed the Far East of Eden franchise) because the console is dead in Japan and the western audience let the developers down, hard.
Square's last stand on Microsoft consoles was on the
Xbox One. After Final Fantasy XIII's trilogy, they still brought Final Fantasy Type-0, Final Fantasy XV and the sales were still not satisfactory enough for that first batch (Type-0's performance in Japan convinced them to drop the console there for good), not to mention Microsoft's retarded policy of not allowing late ports at all (unless Microsoft is the one desperate to make them happen, as seen with NieR: Automata) so bringing the older games simply wasn't in the cards.
Microsoft is sadly still a non factor for Japanese RPG developers. Western consumers won't support them on their systems, and the console is such an abject failure in Japan even Steam is doing far better than it there (respectable numbers even). Microsoft's minimal print run, content policies for late ports that extend to what content the other versions get and their lack of support for publishers will ensure that will remain the case.
The only Nintendo consoles where ports of these games were
viable enough, (meaning powerful enough, and commercially successful enough,) were
the Wii and the Switch. For whatever reason (most probably Square's relationship with Nintendo at the time) it only got side games, a very rushed final Final Fantasy Crystal Chronicles (because Square simply didn't care) and games relevant to the Japanese market (DQ, Chunsoft's Chocobo's Dungeon) and that was it.
The Sony exclusivity theory could be still true.
It was confirmed that Square and Sony signed
some exclusivity contract of some sort keeping their games (at the very least those made for the PlayStation 1 during that timeframe)
console exclusive to the PS1, and that included new Final Fantasy games even at the time X and X-2 was pumped out. The
Bandai WonderSwan handheld did receive Final Fantasy ports for 1, 2, and 4 (3 was planned but cancelled) to compete against the Game Boy Color and destroy it, but the device itself had Sony's blessing and those were older games.
After the GBA came, Square wanted to port those ports but Nintendo (Yamauchi) wouldn't even give them the development kits (they already told them to go and never come back after FF7, which was actually Square's fault because after they parted ways with Nintendo on good terms they started convincing other developers to drop the N64 for the PS1) unless
they did a Final Fantasy for the GameCube, and
after the former executive who signed the PS1 exclusivity was gone. So they set a shell company to "develop" and publish the game, and licensed the Final Fantasy name to it, in order to make Crystal Chronicles 1, a Nintendo-exclusive.
Whatever exclusivity clause was there was no more for future games by the time FF3 and FF4 were remastered on the Nintendo DS and FF11 ported to X360. But it might have been still a thing for the previous games made in the PS1 era.
Moreover, Nintendo's "solution" to get Final Fantasy games again on their
home consoles was not a good one in the long term by any stretch. They basically
humiliated them into making two Crystal Chronicles games. Square just rushed the Wii one, and did the bare minimum amount of support, to just focus on the lucrative handheld market on GBA and DS with the bulk of their Nintendo third party support. It's worth knowing Yamauchi was still influential in Nintendo's decision making even after his retirement, well into the DS and Wii era.
One important exclusivity area: The godawful European translations for Final Fantasy VII were done
by Sony, by the way. This might mean the game will finally get a proper retranslation.
It
is still surprising to see most of the main Final Fantasy series on Nintendo consoles today (just like all of the Dragon Quest series is on theirs). You'd think with Sony's recent aggressive bankrolling and exclusivity deals for Final Fantasy XV, VII's remake, Dragon Quest XI, and Monster Hunter World, that Nintendo would get less support than before.