[citation][nom]Vladislaus[/nom]A tablet is not a portable gaming system, and never will be. Not to mention that the hardware on the PS Vita is still more powerful than most if not all $200 tablets. Also, most 200$ tablets don't have 3G.[/citation]
The Vita's hardware may be more powerful but the Vita is tied to a closed and expensive ecosystem. ~$200 tablets like the N7 may not be uber-powerful but they still got pretty decent 3D capabilities.
While I am not much of a fan of on-screen controls either, I am not much of a fan of paying $20-50 for a traditional console game when I can get a similar entertainment value (albeit of a potentially different nature) for $0-5 on a tablet or smartphone.
As for 3G, how many people would ever bother getting a data plan for a game console? For most people, this makes it a non-feature. Bluetooth tethering and WiFi make a lot more sense and most $200 tablets can do that.
Sure, tablet/smartphone gaming may not be quite the same as gaming on a device with physical buttons but phone/tablets are still consuming an increasingly large chunk of the mobile gaming mindshare - people only have so much time and money to spend on entertainment, regardless of what form it comes in.