Custom Raspberry Pi emulator ($40-$100)
The Raspberry Pi's a popular mini-computer among techies due its small size, versatility, and low price point ($40 to start). There's a lot you can do with it, but what makes it an NES Classic-killer is its ability to run emulated ROM versions of video games -- and not just NES titles, either. This thing can play anything from Atari 2600 and Sega Genesis to N64 and the OG Sony Playstation. It'll even run Kodi, for all your black market Netflix needs.
If the idea of building your own retro gaming console doesn't sound appealing, rest assured that you can pick up a fully configured Retropie (with two controllers) for about $100 on eBay. Otherwise, you can go the maker route and set up the damn thing yourself for a lot cheaper.
Note: The ethics of emulated video games can be a bit fuzzy, so we'll go right out and say it: downloading games you do not own is piracy. That said, there's a potential fair use argument to be made for downloading ROMs if you already own a copy of the game in question, so the choice is yours.