The Titanic was the largest ship at the time, "unsinkable", on its maiden voyage, carrying some of the richest people in the world, greatest maritime disaster at the time, still basically at #2 after more than a century, and the wreck lost for 70 years. The story is definitely more sensational and mysterious than other sinkings.
The 'Wilhelm Gustloff' had at least 4000 casualties in 1945. I believe the memorability of the Titanic is only loosely coupled to the number of casualties .
I included the casualty count as a response to the article quote in OP's comment:
> So why did the Empress tragedy, which claimed even more passenger lives a little over two years later, fail to embed itself in our collective national consciousness?
The Titanic sinking caused ~50-60% more casualties. But casualty numbers alone are probably not enough to make either of them memorable. But an "unsinkable" ship, biggest ever, carrying the worlds richest, inexplicably sinking on maiden voyage and disappearing for decades is a very powerful story.
