So my current Wii U stack:
Besides Monster Hunter 3 Ultimate, I am struggling to come up with any other physical releases I want to add to the collection. There are some games I wouldn't mind playing again (ZombiU) or trying out (Need for Speed, Mario Party 10), but I'm satisfied with what I have unless I find some bargains. The Zelda HD games I don't need as I have them on the original systems (plus they ruined Windwaker's graphics, imo). Splatoon would be cool to have again but the online will close eventually (if it hasn't already) so it- along with many other online-centric titles - would be a waste of money.
I think I will grab the Mario Kart 8 DLC because it would be cheaper to download that instead of purchasing the game again on Switch.