matmico399 wrote:It all depends on what you really want.
Best. Advice. Ever.
The NES is three decades old, and there are lots of options for whatever your tastes are. From legal "NES on a chip" systems (Retron 3), to emulator systems (Retron 5) and classic ones, so many choices.
Nostalgia or just learning what it was really like is awesome. There is something about consoles like the Colecovision, the size of a small bus when you plug in all the extensions and driving controller - that is an experience in itself. If you really want to play on classic consoles though, then be prepared for the occasional controller and hardware failure. They happen. Also, gaming was more limited, so be prepared for the lack of a pause button, no save states, RF output, etc.
In my opinion, having a modern version is an attractive option. My Retron 3 gets far more play than my original side-loader, even after replacing the pin connector. It works well enough for me, plus its a one-stop shop for playing my Genesis and SNES games without any fuss. Get some good controllers though - vintage controllers are pretty robust with some cleaning, although there are modern ones that are pretty good (but the cords are pretty short for some reason). Stay away from IR controllers, like the packaged Retron 3 controllers, for a variety of reasons such as build quality or having to stay pointing toward the tv.
If you just want to have fun with some NES games, there are even 'famiclones', that come with a giant famicom pinned multicart of lots of games. Many of these are infamous for somewhat misleading packaging and promoting far more games than they really have (999 games!), and other issues, but famiclones are kinda part of the NES story. Are they grey market - well, you can buy them on Amazon, so there you go. They are often notable for coming with a light gun (only work on CRTs) or having a controller that looks like its from an N64 or PS1 or something. Beware of their poor build quality, small size, cheap controllers, and may smell of molded plastic at first, but don't let that dissuade you completely. Think of them as a NES sample pack.
The last part of your question was about 'or should I stick with the Genesis and SNES'. Again, I would agree with Matmico's advice of what do you really want? Think about the games you might like to play? The console might be just a small investment compared to the library you build. Then think about how to get those games - for instance, my version of Chrono Trigger is a DS port, not the SNES original. I have lots of cartridges in very used shaped, but I am not the same kind of collector as others on this forum.