To me with a triple vote the answers are overwhelmingly 1, 2, and 9. Nothing else even comes close, in my book. But I would struggle to pick which one of those three sucks the most. I think 9 is a far bigger, more incoherent mess than it's prequel competitors in suckage. They chased a MacGuffin to find a MacGuffin, and one of these MacGuffins worked on a principle of standing in the one particular place she happened to stand, something even someone whose entire education was Lucasfilm movies would instantly recognize the problem with, because it's the reason the Nazi copy of the Staff of Ra didn't work in Raiders. But I still find the movie more fun to actually watch than the the prequels.
On the prequel side, I have a lot more nostalgia for the, if nothing else, memorable episode 1 than the forgettable episode 2, but episode 1 had both lots of Jar Jar screentime and the introduction of midichlorians. Midichlorians ruined the magic of my space wizards, and upon reflection, whereas at the time I gave their introduction some benefit of the doubt as something that might pay some sort of dramatic dividends, I'm now pretty sure their only meaningful plot function in the whole saga was letting Qui-Gon scan Anakin for jediness on his jedi tricorder. Episode 2 seems to just be filler; I struggle to remember it.
I'm going to assume whoever chose Empire Strikes Back is just overcompensating for what they view as excessive praise. That's the same sort of relationship that tempted me to include Rogue One (the Star Wars movie I find fine but nothing special, yet everyone else seems to want to insist it is the gold standard for Disney-era Star Wars). But this isn't a "most overrated Star Wars movie" poll, it is a "worst Star Wars movie" poll, and while there are sustainable arguments for Empire not being number 1, there is no way it is close to being at the bottom.