This absolutely has to be the Starbucks with the coolest view I have ever been to, and I've been to…read morethem all over the world.
I don't make it a habit to go to Starbucks when abroad, and usually patronize local coffee shops more than anything.
But I usually will stop into a Starbs once in a while to grab something similar to what I'm used to at home.
This Starbucks spot is right in the Grand-Place (Grote Markt) plaza in Brussels.
While you sip your coffee (if you don't take it to go), you'll have views of the Brussels City Museum/King's House, the huge spired Brussels Town Hall, and tons of other Gothic architecture buildings.
Aside from building views, the plaza is packed with people shopping, horses, artists, and many other sights to see and people watch.
So, as I said, if you're looking for a Starbucks to visit in Brussels, this is the one with the best views (and it's right in the city center, so you can't get much more central than that for easy access!)