Yes, smartphones certainly have the processing power to handle hardcore games, but they're not built for gaming. Handheld systems like the 3DS are built specifically and primarily for gaming, unlike smartphones. Also, the controls... Handheld gaming systems actually have buttons for controls, whereas smartphones...don't. Instead they use their multitouch screens as the control input, which works, but...not as good as buttons. Now, there are quite a few smartphone games that make great use of the multitouch controls, but when you think about it, most of them would work just as good, if not better, with button controls, stylus controls, or a combination of the two (and this is proven by a number of smartphone games being ported to DS, such as Plants vs. Zombies, Angry Birds, etc.).
And, yes, stylus touchscreen controls are different from multitouch controls. Though multitouch controls work very well for smartphones, tablets, and computers (I freaking love the multitouch gestures on my Mac), they're not really the best for gaming, or at least hardcore gaming. Why? Because you're fingers are blocking the screen! Now, some more casual games can be played with multitouch controls very effectively, but with more hardcore games, often times your fingers just get in the way of the action. Not to mention that you're given virtual on-screen buttons to press, which take up even more of the screen, and they don't feel as good as using real buttons, nor are they as precise. Have you ever used a virtual "analog" stick? They suck!
Anyways, I think you can see what I'm getting at. With multitouch smartphone gaming, your view of the screen is obstructed with your fingers and on-screen buttons. But with traditional handheld gaming systems, you have real, physical buttons to press that are precise and satisfying, and a full screen to enjoy. And in the case of the DS and 3DS, you have a stylus-controlled resistive (non-multitouch) touchscreen, which is better suited for gaming for multiple reasons. For one, because there's no multitouch, and because of the fact that you already have physical buttons, no game is ever going to give you virtual buttons to press. And when there is input to be made on the touchscreen, most of the time it's just a little tap, stroke, or slide, which hardly obstructs the screen. And even if you were playing a touch-heavy game, you're using a slim, compact stylus, not your thick finger(s), so screen blockage is minimal. Besides, in most games, most of the action takes place on the top screen, with the bottom screen being used mainly for menus, commands, etc. (in other words, nothing that you would really care about having blocked from view anyway). This is especially true for the 3DS, as the top screen is the 3D screen, which will most definitely display most of the action. That's the beauty of having two screens.
Now, I realize that the PSP2/NGP does have buttons in addition to a multitouch screen and pad, so a lot of these arguments aren't valid concerning it. But at least one point is still valid, and that's the fact that with any multitouch controls, chances are you're going to be blocking your view of the screen from time to time with your fingers. And the PSP2/NGP doesn't have the advantage of having a second screen like the DS/3DS. But that aside, the PSP2/NGP does have the capability of providing hardcore games with minimal, non-intrusive multitouch controls, since it does have buttons and the touchscreen doesn't have to be used as the only control input, or at all. But will the developers see that, or will the PSP2/NGP's (hopefully larger than the PSP's) library be flooded with casual smartphone-like games and App Store ports? Only time will tell, I suppose. I'm not gonna knock it before it's even released, though. I'm only commenting on its similarity to smartphones, which I dislike. That doesn't mean it will be bad, though. I'll give it a chance to prove itself...or fall flat. Of course, I'll probably never get one myself anyway, just because most of the games that I like aren't available for it, but that's a whole different argument.
