Quite means "to a considerable extent or degree."
This is quite interesting.
Much can also mean "to a great extent or degree," and far can mean "much," but you can't always just replace one word with another.
We do not use "much" or "far" before adjectives in their positive forms (interesting, quick...) but only before their comparative forms (more interesting, quicker...) (Macmillan Dictionary). So you can say:
This is much (or far) more interesting.