Firstly, both list and listing are commonly used as count nouns, and they are synonymous.
But secondly, though their denotations are virtually identical, in some situations, one is easily the preferred choice.
a shopping list
Consistently ranked in the top four of the Financial Times listings
The Cambridge Business English Dictionary largely emphasises the synonymity:
listing noun [C]
a list, or one part of a list:
Here you will find a comprehensive listing of all transportation websites.
Do you have a phone listing for A. P. Morrow Inc?
though the Cambridge Advanced Learners Dictionary & Thesaurus points out what it sees as an additional requirement for 'listing' (and adds the 'item on a list' sense):
listing noun [C] (RECORD)
a list of information that is published regularly, or an item on this list:
I'll check the TV listings to see what's on tonight.
The site maintains a listing of free events for children in the area.
Both 'list of NP' and 'listing of NP' are regularly found.
I'd say that the difference is essentially one of register (as in the first examples): mundane / naive vs 'advanced' / sophisticated / official (wannabe?) / technical. 'TV listings' is doubtless an appeal for respectability.
The choice of the ing-form variant where both it and an associated 'normal' noun are available often stresses the action rather than the article / deed ... (eg 'walking [is good for you]' / 'a walk'), but here I believe that nuance is eclipsed by the formal / informal flavour.