I have every Combat Mission (version 2 now) made. Been playing them for 20 years now, they're excellent. I have three games going against human opponents right now, my most interesting is a WW2 battalion sized fight for the streets of Achen, modeled in incredible detail from real maps.
There is a ton of things going on under the hood that make infantry behave realistically, and armor ballistic vs. armor calculations that rival steel beast.
The modern version, Shock Force, has the drawback that most map sizes are too small for modern tank combat.