Maybe this question is inappropriate for such a high brow group of Redditors, but I am serious. I used to love Caesar 3 for the PC and it got me interested in Roman History. I am skeptical as to how realistic it was, though.
Here's a link to an earlier thread, with a few suggestions.
Apparently the Total War series is decent, and a lot of the maps from the COD series are pretty accurate. If you've played Modern Warfare and then looked at pictures of Prypiat, it's uncanny.
While not very realistic, if you want a fun historical video game that you haven't probably heard of, look for Sphinx and the Cursed Mummy. It's one of my favorite childhood games, combining various elements of Egyptian mythology with some very cartoon-like characters. You'll recognize names like Imhotep, Horus, and Osiris.