It's a horrible, stupid and meaningless phrase which should be outlawed - it is usually spoken by people who have been taken in by the publicity machine and spent money on a movie, only to feel cheated because they don't like it.
Fine - you don't like it.
But worst movie ever?
It's people that use such phrases that just don't understand the concept of a personal opinion - to them everything has to be an absolute. They don't like a movie, then it's crap. Not 'I thought it was crap' but 'it's crap'.
What qualifies a person to make that statement? Actually, you can have a bit of fun with such people when you press them on the actual reasons WHY they thought it was crap - because when you do, it soon becomes clear that they cannot express their feelings in any other terms, and they will usually come back to 'I just thought it was crap, ok?'
Tht's why you get these idiots on IMDB who feel like they have to 'kick against the system'. A movie is critically lauded and gets strong word of mouth from the public, but they don't like it. So they feel inferior, they feel like they are outsiders and there must be something wrong with them, because they cannot apparently see what the majority of others see in a movie - and that manifests itself in a spiteful way.
In fact, I would go as far as to say that no one even has the RIGHT to make such a claim. And that would include the most knowledgeable film critics and historians.
Yes...let's ban the stupid phrase along with 'there's 2 hours of my life I will not get back', and 'Is it just me/am I the only one who does not like this movie?'