I prefer a protagonist with a personality that perfectly suits the game being played. For example, some games require a kind, tsundere, yandere, Kuudere, strong, tough, friendly, etc., female protagonist. In my opinion, when a protagonist lacks personality, they lack essence, which can completely ruin a good story, turning them into a mere presence and implying that they could be replaced with anything, even a rock, because they have no impact. On the other hand, with a predefined personality, it's even justified because people fall in love with them.
The only exception to this rule is short otome games.