Although my main interest has always been football games I have always considered Midwinter to be the best overall game ever made for the Amiga. It is an openworld strategic action adventure set in a frozen post-apocalyptic open world. The open world is an island of 410.000(!!) square km. You play as the leader of the resistance against the despotic General Masters invasion of the island. There are 32 different characters to recruit to the cause with their own skills and personalities (and sometimes relations).
The scope and the execution of the game is just mindboggling for 1989.