A game is great with a 90+ on Metacritic. That doesn't mean it's your thing, just that it does the job of it's genre fantastically. There's no higher bracket for, like 95+, because the only games that get up that high have some kind of hype or nostalgia factors around them. This is a game you shouldn't try to penny pinch with: just pay whatever the lowest readily available price is and get that game.
A game is definitely worth a look with 85-89 on Metacritic . This game should have your attention. Just because it isn't 90+ doesn't mean it's bad, it just means there are minor imperfections. You shouldn't feel bad about paying full price for this, but only fans of the games will insist you but immediately rather than wait for a sale.
A game qualifies as unilaterally good if it has an 80-84 on Metacritic. That's not to say they're a system seller by any means, but they are definitely good games with value behind them. The kind of game that will pop up in list wars if it's a platform exclusive. Not something you typically buy full price, but no one will fault you for being excited about a good game.
A game is simply a passing grade with a 70-79 on Metacritic . Not great. Not system sellers. Not special. Typically only has "cult" fan followings that focus only on what the game does right, romanticising it in their minds. These are games that are definitely worth your time for a bargain, but you may get a few puzzled stares if you mention paying full price for it.
A game is considered a waste of time and money with a score of 30-69 on Metacritic . Don't buy. Don't worry about it. It's really not worth checking out unless you're a die-hard fan of the IP. Even then, you shouldn't be paying full price for rubbish like this.
A game is absolutely worthless if it has a score of 6-29 on Metacritic . Even if you received it for free, you shouldn't display it. This turd isn't even worth getting it for free, much less paying for it.
A game is legendary if it has a score of 1-5 on Metacritic . Get this game only as a joke, but don't pay full price for it.
A game is a fucking goddamn meme if it gets a Metacritic score of 0. Just wow.