Phone games will never come close to handheld quality games for several reasons
1. They'd never get the budget, phone games sell for 15 bucks at absolute most, so they can't afford to make full fledged games
2. Hardware constants, phones aren't as powerful as handhelds, and even if they get to be the devs will always cater to an older one for a larger install base
3.touch only controls, they suck, you see that youtube video of the guy trying to play sonic on a touch screen, yeah, it works for some games but others it's almost unplayable
add to that phones cost more and it's pretty clear anyone interested in gaming would prefer a handheld
I see you don't own a smarphone!
I suppose I will weigh in as a smart phone owner; these issues are quite obvious.
Massive downward price pressure of the saturated iOS and Android app stores significantly limits the size of budget a game can receive. Also, games on smart phones also have very little visibility, trying to be the top 100 out of the +500,000 is never easy. Also the average smart phone game makes about $4,000 total revenue; even the entirety of the Angry Bird brand's total revenue just reaches ~$75mil and trying to repeat such large level of sales is not likely for most genres or games.
Hardware being fixed for a long period of time is a good thing. This means what you invest in today will continually have optimized software produced for it for a longer life cycle without you having to further investment in new hardware. More optimized software = Good
Smart phone controls are quite limited in comparison to to the breadth and depth of opportunity the Vita offers to developers to explore new, more fun, more interesting, or more engaging ways to play. Developers in tern have less constraints on what gameplay experience they can create.
Smart phones have additional constraints on hardware having to share a large amount of resources with the OS and more importantly the battery.
Portable gaming on a separate device mitigates these issues.