That's the point in time where you could see the most clearly which manufacturers had their house in order in terms of weld cleaning, seam coating, basic material procurement and surface protection.

Some of them failed horribly, which led to some brands (for instance: Mercedes) having an undisclosed hit against their earnings to deal with the resulting rust issues on relatively new cars. It wasn't rare at all to see an early 2000's C-Class in the shop for the replacement of four doors, bonnet and rear hatch. And it wasn't rare to see them completely rusted out either a few years later. From Q1 2003 they galvanized those panels and then the problem stopped.

So everybody smartened up and now things are much better, to the point that there hardly are cars made that have serious rust issues. Coatings are a continuous materials science development front and some of the stuff that happened in the last decade and a half is extremely impressive.

Car bodies used to be gone long before the engines, those days are over.

VAG, Volvo, Mercedes, BMW all have a very good reputation nowadays for being rust resistant, I would not know of a favorite between those. By the way, Volvo is now Chinese (bought by scooter manufacturer Geely).

My own car is a 1997 (just before they switched paint formulation for that particular brand) and there isn't a spot of rust on it and as far as I know it has never had body work done. (Don't get me started about engines though...)