I am a huge fan of FM synthesis popularized by the DX7, but the DX7 is only one of many highly influential synthesizers, and FM is only one of many influential synthesis approaches including modular, subtractive, additive, sampling, wavetable, hybrid, phase distortion and various forms of wave shaping, physical modeling, and others.<p>I would rank many other developments such as modular synthesis (e.g. Moog - think Switched on Bach etc. to modern Eurorack), subtractive analog (e.g. Sequential, Roland, Oberheim, etc.), hybrid and digital synths (e.g. Roland D-50, Korg M1), cheap Casio synths (from the VL-Tone to phase distortion), samplers (e.g. Fairlight, Emulator, etc.), analog (TR-808) and digital (Akai MPC) drum machines, not to mention monster systems like the Synclavier, supersaw synths like the JP-8000 and Access Virus (basically the sound of trance) as well as the rise of virtual analog synths, software instruments/plugins, and DAWs to be similarly groundbreaking and influential. In many cases these instruments were keys to the development of genres of popular and electronic music (e.g. hip hop, techno, trance, modern EDM, etc..)<p>For 1980s popular music (and radio recognizability for instruments of that era) the DX7 should probably share the spotlight with the Sequential Prophet 5, Roland D-50 and probably others.