Yes, they are fairly tatty. Even Brussels Zuid (which has a great concourse area) is badly in need of a few coats on paint once you go up the escalators and onto the platforms.
I travel on the Brussels-Oostende route a few times each year. Oostende never looks too bad, simply because of the magnificent frontage, but Brugge station has obviously seen better days. Gent-St-Peter looks like a ghost station, which hasn't been used since World War II.
Stations in many other Western European countries are fairly similar, due to a lack of government investment. While there are many critics of the UK's privatisation of the railways, it has resulted in some decent stations, with modern facilities. (Try finding a cash machine at a rail station abroad. London's mainline stations have roughly one machine, inside or outside the station, for each platform. Paris Nord, with about 50 platforms, has just one cash machine for the entire station!)
Chris