I just leave this game suggestion there for when the day arrives and Bizhawk finally officially supports C64 emulation
The Sacred Armour of Antiriad:
This is a metroidvania game that predates Metroid. You are a human living in a post-civilization era after mankind destroyed it in stupid wars. When aliens invade the world and enslave humanity, your only chance of salvation is to search for a legendary armour that was often mentioned in the tales of the elders: the armour of Antiriad (a corruption of the word anti-radiation). However, you will also have to find some missing pieces to restore it to full power, so that you are able to blow up the alien headquarters and bring freedom to your species.