haqqaton
On the Wii U you have to look away from the main screen to see important information. The HUD is a goid thing that is being implemented everywhere from fighter and commercial jets to street cars. Nintendo is moving backwards!
I prefer the older method plus HUD many games are removable or customizable see PCARS, Minecraft, DriveClub, Infamous: Second Son, NOVA 3, RR3, Zen Pinball 2, Killzone: Shadow Fall and Killzone: Mercenary just to name a tiny selection. In reality if your looking away from the main screen your not paying attention it anyway - It's the same as pausing the game. Holding the Gamepad up infront of you is just turning it into a clumsy opaque HUD - sounds pretty counter intuitive to me.
Zombie U would run just as well on PC, PS4, XB1 and Vita even without a second screen. Look at ACIII which had clutter and a mini-map even though the map was displayed independent of the main TV screen.
As far as Stealth Inc 2 it looks like a Wii U exclusive, but it would play exactly the same on multiple Vita's through AD-HOC and possibly mobile phones too.
The Gamepad is cool, but Nintendo hasn't proven it to be a necessary tool that completely changes the game.
Also it's is worth noting PS3's 3D support and simul-view which I've horribly misspelled this allows for two players to see two different full screens on the same TV! It doesn't allow for the same freedom that a mobile touch screen controller allows, but MP and Co-Op are still achievable on one system using one 3DTV. Many Sony 3DTVs support this function as well as a a few other manufacturers 3DTVs.
Sony proved Vita can do things no other system can with "Cross-Control" on PS3 and games like Tearaway exclusively for Vita. Nintendo needs to do that for the Wii U or the Gamepad will always be an unnecessary pack-in attachment.