Sorry for the OT, and I'm very, very positive about Switch as a whole (less about Western third party support early on and especially later on...even if a bit more than before the reveal trailer even if just due to Skyrim), but I need to stress out how that Wii U support slide...is not actually related to Wii U.
It comes from the final moments of the E3 2011 Conference, this is the actual timestamp when they start to appear
https://youtu.be/p1JJPkd4Q28?t=1h9m36s
If you see a few seconds later, several game logos appear on the same titantron, games for Wii/DS/3DS that were playable on the showfloor for that E3. Well, if you check carefully the games, you'll see that they're all from the publishers that appeared in that "slide". Among them, Tetris 3DS explains the "strange" appearance of the Tetris Online company in what was believed to be the first Wii U support slide.
So, no, that is NOT the Wii U version of Switch's Partner Slide. If you want to compare it to something Nintendo actually put up officially, there's the developers/publishers slide at E3 2010 for 3DS, which was richer than this titantron slide, but still not as much as Switch's (and not by a small margin, even excluding middleware companies).
I hope this post is actually read this time, so this misconception is actually defeated once for all.