the wii us processor is is 3GHz, and the tablets resolution is 720p, so still ahead at least in the procesor. Like mentioned before you still need a remore to be able to play thats another ~$50, then theres game, assuming a quality game thas at least ~$30 dependin on the age, so the shield is up to $380 so far.
Finally the holly diferiantor is that most likely the shield is usseless without a pc to actually play the games, cuz the tablet is just streaming, then thats got to be at least $400-500 to have a pc that plays wii u level of games. so this is like a $780 investment, so still not even close.