There's nothing that came out in the last 20-30 years that could be considered the worst anything (except maybe worst of the last 20 years
). 40's, 50's, and 60's now, that's different. Between Elvira, MST3k, Joe Bob Briggs, random blockbuster rentals, TNT's 100% weird, USA late night and rifftracks, i've seen 1000's of the most horrible creations to come out of hollywood.
ofcourse quite alot of them are entertaining in their own right, some are even ambitious, The Crawling Eye (an early MST lampoon) actually could have been a decent movie save for a few flaws. Plan 9 is hilarious. and Most of Roger Corman's stuff is fun.
One movie i was disappointed in though was Skyline. Now, let me be clear, i had heard people complaining in a general way about it. and watching it i was thinking, whats the big deal? its actually pretty decent. the effects are good. I liked the fact the premise is really a big 50's sci-fi homage. Hell it somewhat reminded me of "Destroy All Humans!", a great game. i was getting into it, i was rooting for the characters, even the main dude who i thought was a douche at first. I saw some of the events coming and was glad they did, i WANTED those things to happen. and as it went along i was getting on the edge of my seat. and just as the movie was about to reach a whole new level of badassery, just as i was out of my seat going "**** YEAH!", just as i was about to become the champion for this movie, telling people "are you ****ing crazy, that was badass". the credits rolled. "WHAT! YOU HAVE GOT TO BE ****ING KIDDING ME!? NO ****ING WAY YOU CAN END IT THERE! THERE?!!" it ends 20 minutes before the story is finished. Its like ending District 9 just as he's getting into the mecha. its like ending Aliens on the line "Get away from her you BITCH!".