Not THE worst ever
But I think it's the third worst, right behind Monster-A-Go-Go and Birdemic. At least Manos had some sort of a coherent plot and a decent ending unlike M-A-G-G, and the acting, sound, and direction wasn't nearly as atrocious as Birdemic.
But it does deserve its spot in the bottom 100 and ranking as one of the worst movies ever.
Just my 2 cents.