I picked up a copy of Ancients in 1986 when it was still published privately by William Banks, based on a magazine review.
What appealed to me then is what I still like about the game: It manages to depict the most salient features of pre-gunpowder warfare accurately with a minimum of fuss.
While a simple game, it's not a simplistic one and by a careful selection of combat factors and a minimal amount of rules the game works as a simulation and a game.
These days most of the boardgame action is in the Commands & Colors: Ancients series, which provides a more colorful and enjoyable game, although not necessarily a more accurate simulation than Ancients.
The original game had just a dozen different types of units and those proved enough to cover all the bases. When 3W republished the game they added some naval units and rules and tweaked the land rules a bit, but made no substantive changes to the land game.
Banks released the design into the public realm a few years back so now anybody can make their own copy and it's still well-worth adding to anyone's collection.