How good is the HST compared to ground telescopes? The Hubble Space Telescope (HST) is a remarkable device. It produced (produces) images whose resolution and clarity were a step change ahead of anything that could be captured from the ground. Is this still the case, or have adaptive optics and ever larger mirrors caught up with the image quality the HST can achieve? Is it still true that the HST's images are better than anything produced on Earth?
Adaptive optics techniques have only been successfully applied in the far red and near infrared. HST produces images with spatial resolution equivalent to ground based adaptive optics images, but it works at near infrared wavelengths and visible wavelengths.

The spatial resolution of HST at visible wavelengths has not really been matched with ground based telescopes. "Lucky imaging" has shown some promising results, but even here, this is usually applied at far red wavelengths.

Except now see this How did VLT&#39;s adaptive optics obtain this resolution for Neptune? Is it really working in visible wavelengths? Progress occurs! (Though it now seems my statement above should only be slightly modified, since the picture contains no information shortward of 550nm and is largely dominated by light at 600-920 nm).