If you spend any time on the Internet, you'll see someone arguing over whether it makes sense to judge something like art/a TV show/a book "objectively."

It is gibberish to say that art or entertainment, in any form, can be objectively measured.

You need to be able to quantify something for it be objectively measurable. One show has twice as many episodes as the other. This painting took three days to make. This movie had a budget of $1 billion. These are objective measures.

It is not objective to say that One Punch Man has better animation quality than Log Horizon. You might believe it's true. 99% of people might believe it's true. You could objectively say that 99% of people prefer One Punch Man's animation (probably not true, but roll with it). It's even possible that every single person except for a guy who hasn't even been born yet believes that it's true. However, if someone were to say "No, I disagree, I prefer Log Horizon because One Punch Man is too flashy!", they wouldn't be objectively wrong, like they would if someone said "Log Horizon has fewer episodes than One Punch Man does". Just because a lot of people hold an opinion, or just because you really really believe that your opinion is right, doesn't somehow turn your opinion into a fact (subjective -> objective). As an aside, I would not be surprised to hear someone say "Twilight is better than War and Peace! War and Peace is so boring, I found Twilight way more entertaining!" You might think that person is an idiot; you might think their opinion is worthless; you might completely disagree with them; but the fact is, neither of you is right or wrong. By the way, slightly off-topic, it's incredibly closed-minded to believe that your opinions are facts and people who disagree with you are wrong. It's easy to believe that sort of thing when you're in the majority, but I'm sure hope that if everyone suddenly decided they hated your favorite show, your opinion wouldn't change on it; it'd still be your favorite, and it would still be great.