Modder zomprd has been upscaling parts of Diablo 2 (opens in new tab) and is planning to eventually release a demo containing a playable slice of the game with sharpened graphics. These HQ textures are being generated using ESRGAN, and they sure do look a lot less blurry than the original does at its maximum resolution of 800 x 600.
Now, zomprd isn't working on a full texture pack for Diablo 2 unfortunately, but hopes that releasing a playable demo of one portion of it might inspire others who can do the full thing. Which would be nice.
You can see a gallery of zomprd's work on imgur (opens in new tab), with the new images on the left. They sure do look a lot less like the before images on an advertisement for new glasses.