So, real talk? Most 2600 games are rough, and barring personal nostalgia, there's little reason to play most of them in the age of emulation, especially arcade conversions, which sometimes nail the gameplay (but often don't), and generally have to perform acts of violence on the visuals to make them work with the system and the business realities around their development (i.e. staffing, timeline, budget for ROM chips, etc.).
Some worthwhile ones that come to mind:
- Combat (multiplayer only)
- Warlords (multiplayer only)
- Pitfall
- River Raid
- Pitfall II
- Space Invaders
- The Empire Strikes Back
It's not that so many more weren't fun, or even still aren't in isolation, but it's like we're all the rich fat kid from Pee-Wee's big adventure and have access to every single game on every single system, at least up until the end of the 90s. There's no reason to play the nice port of Berzerk that looks like it does, or play the flickery Pac-Man mess, or even (I'll say it) fight with the groundbreaking but still primitive and abstracted gameplay of Adventure.