re: What's the best way to play classic NES games these days?

Best or cheapest/easiest?

I'd say today the best way is through a MiSTer FPGA box (properly simulates NES hardware at the chip level instead of cutting corners like emulators do), or using a real NES modified with an NESRGB or HiDefNES kit and using an Everdrive cartridge to load ROMs.

Neither will be cheap, and neither are necessary if you just wanna play some Super Mario, but they are the "best."