If the Hubble telescope was ground-based, what existing telescope would it be equal to?
From what I’ve heard (but I’m no expert), it is not possible to get anything near as high quality as the Hubble here on earth. The atmosphere distorts the light enough that the maximum quality images we can see here are not near what we can get from the Hubble.
Oh, perhaps The Bad A. might stop in.
This facility does some petty amazing stuff - well, at least that they’ll talk about with the public.
(Note - you’ll be greeted by a dire US government warning dialogue box when you go to the site. The military is so untrusting.)
Hubble is a rather small 'scope, with a 2.4 meter mirror. There are lots of 'scopes bigger than that.
It does so much better because it’s over the atmosphere. That gives it two main advantages: it doesn’t have to look through shimmering air which distorts the viewing (think mirages), and it can see into the ultraviolet and infrared that the air absorbs.
Now, there are 'scopes with resolution equal to or maybe better than Hubble’s. They use a technique called adaptive optics. I have a page about this.