One Week in Belgium

Ellen, everyone here has their favorites among the cities you named. The Search box will give you some flavor of that. Many people do say that Brussels was not their favorite city. Belgian local trains are cheap, frequent, and convenient (if often crowded.) Any of the four cities you named can be a base, and you don't need to change hotels even once (... but allowing for final day airport travel, if that is the case.) I should disclose that a large number of people consider Bruges to be a dramatically romantic place that requires overnight stays and immersion in the medieval milieu. (I don't agree. My choice is Antwerp, which is good for several days if desired.)

Have you been to this board's host's page:
https://www.ricksteves.com/europe/belgium

Of course your hotel's distance to the train station is a factor. Use the NMBS (train) English page to learn the travel times and frequencies of train. Some people go to Ghent on Monday because the Ghent Altarpiece is a seven-day attraction. But some other places, like the art museum will also be closed.

Edit: It's not well known that Antwerp has a private company bus to and from the Airport, once an hour. It also stops at a hideous chain hotel on the ring road.

Personally I prefer Ghent as a base. Nice, lively historical university city. It's half an hour from both Brussels and Bruges on very, very frequent trains and one hour from Antwerp.

Tim's advice is pretty much right on, Ellen. We stayed in Brussels 1 night on arrival day from the U.S. as we like to dump the bags and get on with acclimating to local time when we get off a plane. We also wanted to at least give the city a brief look-see. You may do it differently and stay there on the night before departure, if you're flying both in and out of Brussels (we were going on to Germany). It's nice to be close to the airport for more leisurely departure days. :O)

That said, Brussels wasn't a fave, although we admittedly didn't have a lot of time to give it. We enjoyed Bruges (4 nights) Ghent (day trip from Bruges) and Antwerp (3 nights) VERY much, and we wished we'd added days for a longer look at Ghent so will be doing that next time! Still, we don't regret the long stay in Bruges as it's one of those places that is lovely in the evenings and early mornings before the day-trippers arrive and after they depart.

By train, Brussels to Bruges is only an hour; Bruges to Ghent is 1/2 hour or less, Ghent to Antwerp is about an hour; Bruges to Antwerp is about 90 minutes; Antwerp to Brussels is about an hour or less so you don't have to spend a lot of time on transit to get where you're going.

How many nights, exactly, will you have on the ground in Belgium? And what sorts of things do you enjoy doing/seeing? That might help when making recommendations.

I agree picking 1 town as a base, and taking the train to see the other cities you mentioned. I would spend a day in Brussels but not stay there.
Bruges fills up during the day with day trippers, it really is nice to experience it early in the morning and evening, when it is quiet. But rooms in Ghent are probably less expensive than Bruges.