I'm sure I enjoyed some PSX games that would have been reviewed poorly if Metacritic had existed at the time... Rally Cross, for example, seems like a game that wouldn't review well but my buddy and I enjoyed it quite a bit. (Edit: Just remembered GameRankings, duh, and the game has an 85% on there, so... Nevermind then? Seems high)
This sounds super snobby but I think my answer is Radiata Stories, which has a 74. I actually didn't like the game at all for the first several hours I played and when I decided to give it one last shot, it totally clicked for whatever reason. In spite of all its flaws I ended up adoring the game in the end. A whole bunch of charm, a really addictive recruiting hook and a fun battle system. Really liked that game