Square Enix is kind of an interesting case study since they had a large volume of handheld titles relative to many other publishers, but it seems to be shrinking. Is that a reality, or a factor of announcement timing? I think it's an open question, but one that's slowly becoming less open.
Actually relative to a launch aligned comparison, SE doesn't fare bad at all and is quite an improvement on last gen.
In 2 years on market:
DS
03.24.05 Egg Monster Heroes
12.01.05 Dragon Quest Heroes: Rocket Slime
03.02.06 Children of Mana
07.27.06 Mario Hoops: 3-on-3 (published by Nintendo)
08.24.06 Final Fantasy III
3DS
02.26.11 Bust-A-Move Universe
11.02.11 Slime Morimori Dragon Quest 3
02.16.12 Theatrhythm Final Fantasy
03.29.12 Kingdom Hearts 3D [dream drop distance]
05.31.12 Dragon Quest Monsters: Terry's Wonderland 3D
06.15.12 Heroes of Ruin
10.11.12 Bravely Default: Flying Fairy
02.07.13 Dragon Quest VII
In 1 year on market:
PSP
09.14.05 Advent Children: Final Fantasy VII (UMD Video)
PS Vita
12.17.11 Army Corps of Hell
12.17.11 Lord of Apocalypse
Now, I also think an argument can be made the state of the industry (at least in Japan) has shifted pretty dramatically from 2004/2005 to 2011/2012 in favor of handhelds, so the better early support makes some sense. But at the same time, I think people are really doing current handhelds a disservice by comparing current lineups to almost a decade of support on DS/PSP without proper context.
edit: for fun, here's the (Enix + Square) lineups for the first 2 years of previous Nintendo handhelds too:
Game Boy
12.15.89 The Final Fantasy Legend
12.14.90 Final Fantasy Legend II
Game Boy Color
09.25.98 Dragon Warrior Monsters
09.23.99 Dragon Warrior I & II
Game Boy Advance
12.20.01 Dragon Quest Characters: Torneko no Daibouken 2 Advance
01.17.02 Snap Kids!
09.20.02 Samurai Evolution: Oukoku Geist
10.31.02 Dragon Quest Characters: Torneko no Daibouken 3 Advance
12.13.02 Chocobo Land: A Game of Dice
02.14.03 Final Fantasy Tactics Advance
Nintendo DSi (DSiWare only)
06.24.09 Dragon Quest Wars
09.09.09 Norori no Game: Chi
09.09.09 Norori no Game: Goku
10.28.09 Hills and Rivers Remain
11.04.09 Space Invaders Extreme Z