One punch man gets called best anime ever by people who barely watch one anime a year and as such have no idea what a good anime actually is. That said it's definitely not bad, it's a solid 9. But it's not even the best anime of 2015.

Best anime ever according to who?I take it this is the internet thing where the people you listen to represent the entire world?

Its great but not the best.

Its one of the best popular anime that is high quality in a while, that's for sure.

I can see why people call it overrated but I still enjoyed it. It's not my favorite anime ever but I definitely had a lot of fun with it.  Though if you're watching it for just the action, I think you're watching it for the wrong reasons

I've seen a good amount of OPM, and it's a pretty funny anime that isn't meant ot be take that seriously.

I'm not sure if overrated is the right word, and I definitely wouldn't call it the best anime ever.

Of course it's not the bet anime ever, that tittle is forever taken by Evangelion. Go watch that.

I couldn't get past episode 3. I've watched too much cartoon network as a kid and the humor is exactly like most things there, except they were actually good.
I could cite 20 better animes from 2015 alone.

Even Saitama knows his show has been overblown out of proportion... 

Only if an A and a Y aren't in the name...