Super Mario Galaxy 2 for Wii had over 1.28 million downloads (yeah, there isn't a way to validate who owned it and just wanted a copy to emulate/etc). That's just one statistic but it's one you can find pretty easily, and of course other Wii games were downloaded, and the ability to mod Wii's which had a crazy high install base on top of that and not require a hardware modification only added to the amount of people who might have been interested.
http://www.eurogamer.net/articles/2012-01-03-the-most-pirated-pc-wii-360-games-of-2011
I guess I'm not really sure where I'm going with this, but it's an interesting statistic and something to think about that happened in the past. It's crazy to me that people are finding a way to emulate the PS3 more than this to be honest. My opinion is that you need to embrace the inevitable, no matter the intention. What truly is going to matter to me is making sure that Nintendo protects their ecosystem and we don't end up with an (eventual) online functionality full of hackers or people playing on emulators with modded games.
It is quite early to be getting into emulation with the system, but also wearing my game preservation hat, it may only be a matter of time until some eShop games are removed for one reason or another - and having a way to start cataloging them would be nice, maybe not right now but in the future.