First and foremost, why so slow? The VC on both 3DS and Wii U are having small "droughts" all the time, and there are plenty of games not released. How much work is it to actually emulate a game when you already have the file and the emulator? I can't say I know much (read: a thing) about how hard this actually is, but still, nothing justifies the low amount of games actually released.
Secondly, the lack of unified account of cource means that we have to buy the same game over and over and over and over etc. While I can accept to pay a small fee on the Wii U to upgrade a VC game if you had it on your Wii, this is only because you can play the original game in the Wii mode. Not to mention that you get some extra features if you upgrade. But it's time to unify the accouts and make our purchases on Wii U eligible on the 3DS as well.
Thirdly, and my main reason for the threads title, the odd choices for platforms to emulate. Currently we can find NES and SNES games on the Wii U e-shop, however they have announched that we'll get Nintendo 64 games and TurboGrafx 16 games later,not to mention GBA and DS games. Soooo, anything missing? Where is the Gamecube? And why not Wii? Sure, the console can play Wii games already, but why not release it on the e-shop?
Now, what feels even more out of place (at least for me) is that while GBA and DS games are announched for the Wii U VC, they are not for the 3DS? The 3DS library is certainly better than the Wii U, but the lack of Pokemon, GBA and DS games is holding back it's potential.
I'm still happy we're getting DS games on the Wii U, I'm looking forward to playing Pokemon (legally) on the big screen. :D