With how many games? How long, on average, their mobile games are lasting? To me it seems SQEX is pumping out plenty of mobile titles that on the aggregate bring a good amount of earning, but overall are inefficiently carried over.
They rank their successful titles as follows:
Release dates:
DQM: January 2014
Schoolgirl Strikers: April 2014
FF Record Keeper: September 2014
Sangokushi Rumble: June 2013
Puzzle Bobble: December 2013
Dragon Quest X: December 2013
Lost Zero: September 2014
It is worth keeping in mind that Square Enix didn't do many f2p games outside of Mobage/GREE until more recently.
That said, mobile games only cost a couple million to make (or sometimes less), and things like DQ, judging by similarly charting titles, bring in around $90-$100+ million a year, so there's a lot of room for failure while still maintaining fantastic margins overall.
By comparison one failed AAA game at $20-$30 million (and that's lowballing it even compared with to what they listed) is like the cost of 10-15 mobile games.
B-tier (presumably handheld? unless they mean like maybe LR but that seems too cheap?) games they listed as $10 million, so we're looking at 3-5 mobile games still.
As for failed f2p titles I can think of a few. There's Agito, Mana, the Cross games and air patrol (they faded along with most old school Mobage games), and the one of the waifu sci-fi titles.
That's not a horrible failure rate overall given the successes.
We'll have to see how G-BIKE and the samurai game do still.