Good locations to stay in Brussels

I did a quick lookup to see where the markets are; the Grand-Place in Brussels and around the Bourse, the Place de la Monnaie, the Place Sainte-Catherine and the Marché aux Poissons. If you triangulate the first 3 places on a map, that’s where I’d look. Either that, or between the Bourse and Place Sainte-Catherine. I’ll be in Brussels in March and there are a number of hotels in that area that I looked up on Trip Advisor.
https://www.brussels.be/winter-wonders-and-christmas-market-2017

I stayed at Ibis Grand Place and recommend it.
http://www.ibis.com/en/hotel-1046-ibis-brussels-off-grand-place/index.shtml

I've stayed at the Ibis off Grand Place which Jazz+Travels recommends and would definitely stay there again. Very close to Gare Centrale, Grand Place and restaurants. There are several hotels which also face onto the Place d'Agora. Ibis is/was the most budget of the selections when I stayed there several years ago but it was modern, clean, well-maintained and had very nice staff who spoke excellent English.

I did not get the breakfast there but walked around to Les Galeries Royales Saint-Hubert and ate at Le Pain Quotidien. Yep, it's a chain but they have soy milk for coffee, lol.

You don't mention a budget. I stayed at the hotel A La Grande Cloche and was very happy with the location. It's just a few short blocks from the Grand Place but in a less touristy neighborhood. Nothing fancy, just a clean budget hotel with a nice staff in a good location.

I stayed at a place called Residence les Ecrins last summer and it was perfect. In the Place St. Catherine area, less than 5 mins to Grand Place, 10 minute walk to train station and a metro station at the end of the street (30 second walk). Residence les Ecrins was comfortable, friendly and quiet. When I was there they had breakfast included and coffee/tea all day. Not sure if they still do this, but I would 100% stay at the same place if I am in Brussels again.