As many people have doubtlessly already explained, the answer is yes and no. Opinions themselves are, by very definition, about subjective matters and therefore cannot be right or wrong. People who say "well that's just your opinion/well it's my opinion so it can't be wrong" are however almost always saying that about a misconception or a conflict of facts which finds them on the side without empirical support for their argument.
If I have the opinion that gravity is a fictional construct fashioned by "the man" to keep us from our rightful place soaring through the sky, I am clearly a crazy person; gravity definitely exists, and I invite any skeptics to test it by walking off of high buildings, heh. You can have an opinion about whether something is "the best" or "the worst", but if you hold an opinion that an event happened at all? Yeah, not actually an opinion. If the thing you're arguing about exists in a environ wherein "the best" can be quantified by statistics, you are also not actually the holder of an opinion - which engine is the best engine is a far different question than which band is the best band.
Basically, anything you can be proven wrong about = not something where you can cite "It's my opinion!" and get away without looking stupid when somebody points out the facts are against you.