I really do think this, the main problem with the playability of smartphone games is the lack of a direction input, not so much the lack of buttons. 

The thing I don't think those bulky controller add-ons with SNES style buttons layout/full size d-pad/analog sticks .... I mean really no one is ever going to really use those. Not one wants a smartphone that looks like this 

The main problem with smartphone games IMO is a lack of directional input. Even a small joystick (Vita sized) or a trackball would make many games far more playable, maybe a form factor more akin to this:

Not one would really look a device like that as anything odd. Maybe you could even add a A/B type buttons on the other side, but you don't need to go crazy with the control input. Even with just a directional input ...

Adventure games, even platformers, racing games, etc. would become instantly a lot more playable and it wouldn't really take much. I wonder if a company like Samsung or HTC will ever realize this. You don't need the kitchen sink here, even just a directional input would be a game changer if was standardized on a popular line of phones (like the Galaxy series). 

http://mobile.geek.com/apple/255748-apple-patents-a-pop-up-iphone-joystick?origref=https:%2F%2Fwww.google.com%2F

If Apple actually ever uses that patent in real life ... it's over for dedicated handhelds. They will have a market of maybe 20-25 million probably almost all in Japan and nada in the West. If Apple does it then various Android devices would likely follow suit to copy them and it would get rapid support. 

Actually I found on screen analog sticks to be quite functional. Problem is that that for most people the fat fingers to screen size ratio is completely off the charts.

For me they just kinda feel off. It's not unplayable but an actual joystick would be a big game changer. 

I hope Apple takes like 50 years to use it.

They probably wouldn't use it on iPhone 6S ... but iPhone 7 ... who knows. People want new things in their phones too there's a lot of pressure on Apple and Samsung to come up with new features that justify a new model. This could be one new feature. 

Battery life. Not control input. My poor galaxy s3 can't even make it a whole day just playing music off the device. These smartphones suck batteries dry and until Samsung or Apple can come up with a decent battery that doesn't die in 10 hours from being idle, then phones will never compete with 3DS or Vita.

@Mods

See? I can make a post and mention Vita and not be mean :P

Just switch to Sony Xperia Z3

I find it hilarious that everyone (smartphone fans and manufacturers, that is) keeps insisting that touch controls are superior to old-fashioned buttons, yet are forced to start emulating or even add buttons and sticks to smart devices due to the lack of input options.
Two steps forward and one back, I suppose.