Sony has in my opinion the most divers 1st party titles and the highest quality on average.
They also have the overall most talented studios.
I can't imagine Microsoft building up such very good teams in a very short amount of time. It takes several years and MS just isn't there yet.
And we are right now seeing Nintendo having a hard time support 3DS and WiiU at the same time. 3DS support is very good, but WiiUs is terrible, I guess they are swamped by HD development. No 1st party launch titles except for a 2D plattformer and a mini games collection and after that nothing for 10 months? Thats just ridiculous.
Sonys is apparantly doing a good job supporting Vita, Ps3 and Ps4.
Even tho Vita comes a little short.
(LBP Karting, GoW:Ascension should've been Vitaexclusives. Would've easily sold more on Vita and would've gotten better review scores. Puppeteer, Rain and GT6 should also be on Vita, not Ps3 only)
Only 2012 till today:
Vita:
Uncharted, Wipeout, GravityRush, LittleBigPlanetVita, PSAllstarBattleRoyal, Sly4, SoulSacrifice, MLB12+13 are the bigger 1st Party titles so far. There are also some smaller ones like LittleDeviants, Unit13, ModnationRacers, SuperStardust and more.
Upcoming: Tearaway, Killzone:Mercenary, FreedomWars, Jak&Daxter Collection
Ps3:
Starhawk, Twisted Metal, MLB12+13, Tokyo Jungle, PSAllstarBattleRoyal, LBPKarting, WhenVikingAttack, Wonderbook, Sorcery, Sports Champions 2, Ratchet&Clank:FFA, GodOfWar:Ascension, SlyCooper, PS Move Fitness and a lot of HD Collections.
Upcoming: Beyond:Two Souls, TheLastOfUs, Puppeteer, Rain, GranTurismo6
Ps4:(announced)
Infamous3, Knack, Killzone:ShadowFall, DriveClub
Those are only titles we know of so far, I think that list will get bigger after E3.
There are quite some Sony team were we don't know what they're doing.
They put out an extreamly good 1st party Support for 2-3 plattforms, thats something neither Nintendo nor Micrsoft can compete with.