What are the top military games that I could buy except BF and COD?

Operation Flashpoint: Dragon Rising and Operation Flashpoint: Red River cater to the ultra-realistic market. At least, it says it does. I don't actually know what a combat situation is like so I can't confirm or deny whether it's actually realistic.

Arma 3 is an option, but apparently that's mostly multiplayer (never played it, I don't care for competitive multiplayer).
 

Bohemia Interactive does cater to a realism market. The AI is great, as is the multiplayer. If you know what you're doing, you do better. If you don't, you play COD.