I can't agree with this. At all.
First off, "the other games are better off on other platforms"... no way. I'd rather play any srpg, jrpg, or drpg on Vita than any other device. I'd rather play most indies on vita than Steam - in fact, I double dipped on tons of games that I already owned on Steam, from Hotline Miami to Binding of Isaac to Risk of Rain to Frozen Synapse and probably another couple dozen. They can sit in my Steam library forever, or I can absolutely love them on Vita... I'd take Vita every time. And despite having access to IOS and Android, I'd take any of those games on Vita first too, due to, well, buttons + touch.
Second, 'most exclusives are not that good'... I don't even know how to approach that. Killzone Mercenaries is amazing. Lumines. Super Stardust Delta improves on Super Stardust. Tearaway! TxK! Demon Gaze. Wipeout 2048.
And there were plenty more that were solid games, like Unit 13 or Uncharted.
Sure, some exclusives sucked... or were just 'okay'... but that's true of any device.