The Rhye's and Fall seems to do a very good job of realism. Stability is freaking annoying though, and as fun as it is to play for historical goals, when my pan-European Germany empire collapses due to 'instability' it's really not fun anymore.
That's when I go back to unmodded Civ.
Also, I prefer to think of 'building a library' as 'building a city-wide network of libraries' or somesuch. It is also representative of generally raising the standard of education/science.
Also as Bushface said, technology advantages should probably play a greater role - realistically, infantry need armor support to stand against armor, and a musket couldn't even damage a tank.
Realism is sacrificed for fun and game balance.
