It is great, and the caveat is that it is great at what it does. It's a comedy series originally drawn in a really crude style, but was picked up by an incredible artist so now it's a comedy series with amazing art and action. The action panels are insane - an example of a gif made with his panels; https://c.tenor.com/pYataaiHwi4AAAAd/one-punch-man-opm.gif

All that to say, if you go into it understanding its a comedy and a play on the Superhero genre rather than being some hyper serious action/drama series it is really good imo.