What is the best way to play retro games on a modern TV?

Three honest paths: original hardware plus an upscaler, a flash cart setup, or emulation on a modern console or PC.

There is no single best answer, but three paths work well. (1) Original hardware plus a video upscaler like RetroTink gives the most authentic experience on a modern TV. (2) A flash cart like an EverDrive lets you play a full library on original hardware without hunting cartridges. (3) Emulation on a PC, Steam Deck or current console is the cheapest and most flexible. Your choice depends on budget, authenticity preferences and how much setup you want to do.