Oh...I dunno. Maybe I'll get get drawn and quartered for this, but I'm not certain that ketchup belongs anywhere!!
It just doesn't strike me as a condiment that compliments (unlike kickass Dijon/Creole mustards, and some mayo), but it just overwhelms anything that crosses its path! Granted, the ubiquitous fries and ketchup combo has its merits, but that largely derives from trying to cover up the "flavor" of the typical cryogenically-preserved fries!! Try hand-cut fries, done proper Belgian style, and I swear that you won't need any masking of the flavor. The fries are a killer way to mop up some of that leftover mussel sauce, too....
When I studied abroad in Italy, a chief grievance of a lot of the school's provincial twits was the lack of ketchup (along with no ice and the lack of English speakers); I think it was during this time that I learned to appreciate the subtleties of different mayo varieties/compositions (well..less Italy, more rest o' Europe), and simple lack of dressings and condiments in general.
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