IMO for the NX to be successful it at least needs to have the newest Tegra chip. The performance for the older one just isnt good enough to run anything modern well. Even in less optimized settings like dolphin it doesnt run older Wii / Gamecube games well.
Doom BFG Edition on Xbox 360 and PS3 runs at 720p60 with frame-rate drops. The same game running on the Shield Android TV micro-console, based on X1, hands in a near-flawless 1080p60 presentation. Trine 2 - another 720p30 game on Sony and Microsoft's last-gen consoles - operates at 1080p30 on Tegra X1. Typically speaking, OpenGL games port really well to Tegra X1, while DirectX ports, like Metal Gear Rising: Revengeance and the recently released Resident Evil 5, aren't so impressive.
Essentially anything more rigorous than an older game tends to not run as well on the older tegra format. Hopefully Nintendo can work their magic or at least find a way to stuff Parker in the NX on the cheap.