If you want a wii u, well then I guess you're planning to hack it. As said already, it has compatibility for wii and gamecube games. The virtual console games can run some custom injected roms with some decent results for compatibility like N64 and DS. For emulators? Well retroarch is a thing, if you know anything about it, not all "Cores" or consoles emulated on it will be available for the wii u. ( I think it's system specific with pc and android having all access vs game consoles having limited access) You probably want to use this instead of virtual console injects, but only for systems that isn't supported by retroarch.
For wii u, SNES9X works well and has support for MSU-1 since it is version 1.60 Genesis plus gx is all you need for all things sega. (No 32X, not like that's a big loss compared to having Master system, Game gear, and sega cd.) Nestopia is good for nes games. There is quite a few to dig into that should run well unless is some kind of overpowered arcade game. Just make sure you have a decent size SD card for it.
Other than those things, the rest of what you can do is probably play modded wii u games. (if any) I mean if you just want a system with old games to play on the gamepad, it helps. Especially if you don't want to use other devices while is charging or something. Or you can do like me and just have it play sound test from your favorite game so you have something to listen to when you're in the room.