My TV does not have a cable in for my Atari. Is there a device that converts from RF coax or UHF to HDMI or other common ports found on flat screens? Is there a aftermarket console that can play the game by the cartridge or use a medium like a VCR?
There are devices that can "tune" into RF Analog signal and convert it to HDMI, for example, this one on Amazon.
It's kinda expensive though if you're going to use it just for playing Atari 2600 games...
Do you specifically need to play the original cartridges or are you OK with just the games?
Atari is releasing a modernized console-like system called the Ataric VCS. It's not out yet, but you can read the details on the Wiki page.