Three contenders, one winner. Which of these three snowstorms was most impressive in the given area that it targeted most, in regards to amounts, dynamics, temperatures, and perhaps other factors too (wind, ice, duration, etc.).
January 10-11th, 2017 (Portland Metropolitan Area and surrounding locations): 8-12 inches of snow in many areas (with higher amounts up to 20 inches in select areas within Portland) that brought along with it thundersnow, freezing fog, and of course a complete forecast surprise.
February 24-25th, 2019 (Eugene and South Valley): Brought 10-20 inches of snow in many areas, creating havoc in terms of power and timber losses. Was a forecasted event, and dropped massive amounts in Central Oregon as well (20-30 inches in spots). Temperature never reached 32 degrees in Eugene during the storm (remained above freezing the entire time).
January 18-20th, 2012 (Puget Sound area and Western Washington): Brought an onslaught of snow (6-12 inches in many locations), followed by an ice storm (0.25-0.75 inches of ice) which crippled power and transportation services for several days. A rather long duration event, that was forecasted heavily and warned in advance.
So, which storm was the most impressive? Dynamics, radar presentation, wind, temperatures, almost anything is fair game. Just remember that your individual location doesn't matter, just the locations in which the storm impacted (all similar PACNW lowland locations).