Final Fantasy XI, Final Fantasy XIV: A Realm Reborn and Dragon Quest X have around a million paying subscribers between them. That's not a gigantic number.
The figures were revealed in the company's annual report, which you can see in full here. They have, at the very least, put some nice background art on the otherwise bland statistics.
Square Enix's president and representative director Yosuke Matsuda said these words in a statement:
(I like to think he shouted the names of each game).
While the figures aren't huge - less than a million between three games, remember - the fact they have a 'solid revenue base' shows that Square Enix isn't worried.
It's good to see, as it shows you don't need WoW numbers to bring home the bacon in the MMO world. You just need to introduce plenty of F2P mechanics, take much-loved single-player RPG franchises and make them into MMOs and/or make an entire game, realise it's a bit rubbish and re-do almost the whole thing while apologising repeatedly.
There haven't been figures released to show the split between PC and console players, but I'd guess the majority of those involved in the three games live in the world of personal computing. Just a hunch.
And PC does seem to be, increasingly, Square Enix's format of choice in some respects.