I would agree that the DX7's sound is really dated has honestly really negatively impacted some of my favorite songs recorded in the the 1980's [0][1], but I really cannot think of an specific instrument as distinctive and widespread as it. The Telecaster and Stratocaster were very popular, but it's very tough to pick them out in a recording from other types of electric guitars. Hammond Organs are distinct and popular, but nowhere near as ubiquitous as the DX7.
[0]https://www.youtube.com/watch?v=JTTC_fD598A [1]https://www.youtube.com/watch?v=zXRLozwejDk