Wonder Boy: The Dragon's Trap (mentioned around the middle) is IMHO a fantastic example on how to modernize an old game.
Not only they reused the original source code, but you can switch between the original and remastered graphics and music at any time, and even separately in any combination. It also allows you to generate a passcode so you can use your "save" with the original game, on top of being able to accept original passcodes as well.
It was a true work of love; the main coder, Omar Cornut, wrote one of the major SMS emulators and this was his favorite game. I suppose that talent like that is hard to find for every single game, though...
Don't look a gift horse in the mouth. I'd take anything free then give it away to somebody else if I don't use it. I have a few retro gamer friends who could give such machines a good home, whatever it is.
FPGAs (and their smaller cousins CPLDs) have been used in a bunch of products, they are not used to implement whole machines usually. The XRGB-Mini has an FPGA powering it, as well as Everdrives. Even the Retro Freak had a tiny FPGA to help dump carts.
To clarify the FPGA is not necessarily a board (its just a component) but the board is what makes one useful for a given purpose. You'd want video out and inputs to reimplement computers and consoles, for example.
That said, my comment was thinking about a broader reimplementation so as to add HDMI out and analogue controls in a whole system. It could easily be a MiSTer core.
Weird. Why a FPGA? You only really need to convert the video signal from the chip to HDMI. Or is that because making it in FPGA would be cheaper than recreating the chip like it was BITD?
FPGAs are better at recreating chips and electronics circuits accurately, and there are several FPGA boards out there it could run on. An accurate open source implementation is also a good way to document the chip for future generations.