Possibly the best Sega Genesis game and easily one of the best strategy games I've ever played, Nobunaga's Ambition is n
The game takes place in mid-16th century Japan during the Sengoku period. Your main goal is to lead Oda Nobunaga and his fief(territory) to conquer Japan and unify it.
There are four diferent scenarios which you can play in. Each scenario ranges in the size of the map, and the starting layout of territory and power.
Gameplay is turn-based strategy style. You spend each of the four seasons of the year(four tuns a year) building up your territories and preparing them to take over the others. Battles are done on a grid battlefield of sorts, where you position your units and try to outwit\defeat your opponent to defend your territory , or take his ... depending on who initiated the battle. You need to develop your land, grow crops, adjust taxes, purchase more soldiers and numerous other activities in order to build up your clan.
This game has massive replay value and is highly unknown. I suggest you check it out.