I just came back from Brussels. We took a late Flixbus from Amsterdam to Brussels which was half the price of the slow train and 1/4 price of the faster train.
We stayed at the Dominican Hotel which is a Marriott property. The hotel is clean and very gothic. They play creepy church music in the elevators and the hallways are dark. The rooms are adequately sized but small and had a small refrigerator. Breakfast was not included for status members but there was free coffee in the lobby. It is only a category 4 and well located near the central train station so it was a good choice.
Our first day in Brussels we went to Bruges and Ghent. Both were incredible and well worth a visit. We took the elevator to the top of the Belfry in Ghent and the views were breathtaking. We did not have time to go inside the old castle that has a museum. It is definitely a solid half day and you could probably do a full day there. Bruges was also well worth a visit but much more touristy. Every store there was a cafe/souvenir shop. I think they also must have really good PR because the city is dubbed the "Venice of the North" but the canals are not really prominent. We took a boat ride on the canals which was really worthwhile.
We at dinner at O Delicis Alice. The food was tasty and well priced. The staff was all really friendly and help translate the french menu for us stupid Americans who only know a few french words.
Our initial plan was to go to Paris for the day on the speed train, but by the time we were able to book, tickets were 200 euro per person and didn't make sense to spend that for the day. Instead we did a half day tour of Brussels and half day in Antwerp. Brussels basically has very little to see unless you want to see a statue of a boy peeing or the EU buildings. Antwerp was interesting to walk around the medieval area and we rode the Ferris wheel. We also saw the views from the MAS building and walked around the train station area. We flew out from BRU at 6 am the next morning.
My honest opinion of Brussels is that it feels like the dementors live there. It is a very dreary city. While there are plenty of things to fill your time with, I would say see Bruges and Ghent and then move on, unless you have a reason to be in Belgium otherwise. You can probably even do Bruges and/or Ghent as a day trip from Amsterdam but it would be a very long day.
I'll try to post some pictures later. If there is anything specific anyone wants, let me know.