doesn't matter. it was successful in NA, and continued to be successful over time. It also got... dun dun dun, good reviews.
CoP was its shining star. The story was epic, had TONS to do (was like 50times longer than this games entire mission set), and is considered to be one of the best MMO stories of all time. The zones were unique, the gear and jobs were cool, etc. Then you have ToAu which again, was EPIC. The zones were massive, well put together, and besieged was amazing. And then WoTG while just a rehash of past zones was amazing as well. Campaign was incredibly fun, the quests and missions were deeper than anything in this game, and the sense of exploration and journey you felt traveling through the war-torn past was awesome.
For story, immersion, and sense of adventure, no MMO has even come close to touching FFXI. Cept now cuz abyssea kinda killed everything lol.