I actually have a bunch of controller appropriate games on my Steam account that I could see working with this. Deus Ex, Batman Arkham Asylum/City, just about all the GTA games, Beyond Good and Evil, The Walking Dead, Fable, Skyrim, Bastion, Space Marine, Super Meat Boy, Assassin's Creed II, Psychonaughts, Saints Row 2, Ghostbusters TVG, Dreamfall and the three Crystal Dynamics Tomb Raider games.
But if you're home anyway why would you choose to play those games on your tiny Project Shield rather than your desktop or HDTV? There's just so many better options.
1.) Play those games on a PS3, 360, or Wii U connected to your HDTV.
2.) Play those games on your desktop.
3.) Use an HDMI cable to connect your PC to your TV and play with a wireless mouse & keyboard on the couch.
4.) Buy a laptop instead of a Project Shield and play those games on your couch.
5.) Buy a Vita/3DS and get access to exclusive portable games that you don't own rather than making games that you can already play portable.
If this thing was $99 I could see maybe buying it (mostly for the inevitable console emulation), but there's no way that Project Shield is going to be cheap. The tech is too advanced and Nvidia can't sell the system for a loss like Nintendo has always done.