Archon for the Commodore 64.
It’s simple, engaging, cathartic and very nostalgic. It also featured a very catchy theme which set the standard for what could be achieved with the C64’s hardware synthesizer at the time.
Once you get accustomed to the patterns its fairly easy to beat but you can make it more challenging/strategic by making it your goal to capture the power points with weaker icons instead of totally obliterating your opponent with the more powerful ones.