I haven't played other 2600 games before, so I'm not sure what its capabilities are (I've only seen footage of Halo 2600 on YouTube before). But this game looks great! The graphics are simple - but I love how chunky and abstract they are! That title screen is quite ominous and sets the mood perfectly.
That being said, there were a couple issues I ran into. The biggest issue was it isn't clear from the start where to go. For example, I didn't know I could enter the house until I walked into the 3 block gap above it. And I didn't know that I had to attack some enemies (like the stationary guy in the Torii gate room).
But once I got past that, the game felt really good, like a Zelda-like as another commenter said. It was really interesting to see level design on such limited hardware. The event where the knight saved me was really cool.
There were, however, some bugs. Sometimes mobs would push me through walls, and I'd have to restart the game. And sometimes I would get stuck on trees. But these latter bugs are minor for a jam entry.
Overall, great job! Excited to see what else you do with this!