I got the Genesis one on Black Friday for about $30, and it was a nice thing to have setup in my bedroom on my old flat screen. (My 2006 model 42" Sharp 1080P HDTV that weighs 78lbs) The kids loved playing a few of the easier games like Ecco and Sonic.
Eventually my mother in law moved out and we couldn't get her tv unmounted from the wall, so I bought her a new one and we set up that room as a guest room/play room for the kids. So I had this crappy little amazon fire tv, so I got the Nes and SNES classic machines and hooked them up to that. Even back then, those were pricey units. I had to pay over retail for them used on eBay. The kids played those a little, but not enough to get hooked on them. I need to go in there and start playing the games more to show the how awesome they are.
I skipped on the Turbo Graphix and Playstation consoles as I really wasn't into the games that much. Plus the Playstation reviews were horrible.