You have to go along way to prove a point. You can't control a pc with a controller unless you install some software that does that and make it auto boot. I imagine navigating a desktop with a dpad can't be too great. If you wanna use a mouse then you have to get a extra long cord that runs to a couch from your tv since your pc has to be plugged into a tv with a short 1 dollar cord. Don't tell me you'd use a wireless mouse cause I had one. You gotta shut it off when you aren't using it otherwise it drains the battery. The slightest nudge activates it again. Good luck convincing people you just gave them a good gift, not the cheapest of cheap pc's. For extra LOL's you should leave the 1 dollar price tag on all the parts you buy for it.
In 2009 I designed a mini ITX PC I called "Consoul" which was basically a homebrew console design:
It ran a hyper stripped build of Windows XP x64 I made with a program called nLite, and was entirely controlled by Dualshock 2s (Later on, Dualshock 3s), using an emulator/media frontend called GameEx.
It emulated over two dozen arcade and console machines (With tens of thousands of screenshots for them all), had about 40 PC games, all my movies/TV shows and music on it. It could also rip DVDs to AVIs (And burn DVDs from existing AVIs), or rip them to ISOs and play them or burn them, rip PSX, Sega CD, PCE-CD discs (And add them to their respective emulator's game list), rip or burn audio CDs as well as play BluRay movies. It also acted like a big ass NAS box on my home network.
All of that was controlled by hitting buttons on a gamepad: JoyToKey was the backbone of a lot of it, along with dozens of batch scripts and AutoIT programs I wrote. The only part that kind of sucked was using a web browser with analog sticks to move the mouse, but I had an on screen keyboard that allowed typing (And later the DS3 bluetooth keypad).
I made a few successor units with better hardware and more capabilities (Giga Drive and Neo Drive), but I guess my point is that making a dedicated emulator box doesn't require interacting with the machine like it's a desktop PC.
I think the total cost was about $400 for the hardware, and required a level of ability and knowledge to create that the vast majority of the world does not have nor would care to have.
So yeah, even after designing things like this I can totally see the appeal of the mini NES. I probably won't buy one, but I can see why a lot of people would. It's ass easy to use, cheap, and probably has at least one or two games most people would remember playing when they were kids.