The launch? PS3, with no question. The launch line-up was pathetic (the main attraction was "Lair" for gods sake), the price was ridiculous, they took all 3rd party support for granted despite contructing a machine with stupid, developer unfriendly architecture and they were even stupid enough to keep the hardware unavailable in their biggest market by far for almost half a year. Atrocious launch.
Nintendo's biggest fault was lack of advertising, hardly anyone knew the thing was coming out. The pricing was good and the launch line-up arguably the best anyone has seen.
Now, had the question been "which console was handhled the worst right after launch?" or "which console was constructed most poorly and forced onto a market that didn't want it?", the answer would be the Wii U.
The launch itself though, the PS3 by miles.