Here, I got one.
Not the worst game that I played. Just the one that I barely got past the start screen.
Ecco the Dolphin. Didn't own it, just rented it. Actually thought is was a glorified dolphin swimming simulator. Never got past Level 1. Didn't even realize there were levels or an actual game to play.
The game had basically no instructions, so I had fun doing flips, eating fish and seeing how long Ecco could hold his breath.
Second one that falls into the category: Friday the 13th for NES. I basically just did a speed run for getting killed by Jason every game. Another minimum instruction game that didn't have obvious objectives.