The DX7 mainly was an affordable all-rounder that got loaded with a ton of already-good presets and a way of managing presets. Yamaha had already released the GS-1 three years prior, but obviously it didn't remain in the books of history quite the same.
The Sega Genesis soundchip, YM2612 is also a great showcase on how different FM synthesis can sound compared to comparable competing consoles.
If anyone is interested, there's a great open source soft synth called Dexed, which is compatible with DX7 soundbanks (and comes bundled with a lot of em). A free, fun way of getting a glimpse into FM synthesis and music production techniques of yore.