81 is a fine score. Would I have liked more? Yes of course, a better score is always nice.
And while the main complaint seems to be 'lack of content at launch' I think it's closer to 'not enough content for the north american asking price at launch'.
Taking Captain Toad as a reference point I think it would have scored significantly higher if it had been 40 dollars / 35€ in all territories, since pretty much every review I saw, even the lower scored ones, acknowledge that Splatoon feels fresh, innovative, has great, addictive gameplay, solid controls and great replay value, wich sure sounds like a glowing recommendation to me.
To me, the testfire was the best recommendation though. I've played it. I know it's great, I'm getting it.