For me, the OST should be atmospheric above all else, even catchiness, which is why soundtracks like Final Fantasy Tactics are top tier for me. The OST fits the scene, and also evokes all the proper emotions that are felt by the characters at the time, such as anguish, fear, suspicion, and so on. Many game OSTs nowadays seem bland by comparison, trying too much to make characters seem "badass" or "cool" or something, instead of focusing on what's actually happening in the game at the time.
Perfect example of what I'm talking about being the Lucavi theme from Final Fantasy Tactics: https://www.youtube.com/watch?v=Gt8CqDjbr3o
The track gives off fear, horror, hopelessness and suspense, as it should. You're fighting other worldly demons who want large amounts of bloodshed. Demons, whom folktales have misinterpreted as being heroes. This is no situation for something catchy or dance clubby, the OST should be working to give the player the same feelings the characters have, and FFT's entire OST does it perfectly.
Perfect example of what I'm talking about being the Lucavi theme from Final Fantasy Tactics: https://www.youtube.com/watch?v=Gt8CqDjbr3o
The track gives off fear, horror, hopelessness and suspense, as it should. You're fighting other worldly demons who want large amounts of bloodshed. Demons, whom folktales have misinterpreted as being heroes. This is no situation for something catchy or dance clubby, the OST should be working to give the player the same feelings the characters have, and FFT's entire OST does it perfectly.