I was in Ghent earlier in the year and made a list of games shops. But, having no intention of returning any time soon (not that it was bad - quite the opposite), I threw the list away.

What I did was go into the tourist information and ask the assistant to copy me the page of the local telephone directory which featured toy and game shops. They were happy to do this, although they clearly had never been asked to locate games shops before! Then I took a tour round the city which passed the locations of these shops.
I can remember there was a decent games selection upstairs in a toy shop with a fairly central location. It's on one of the main shopping streets. They had a good selection, including El Grande before it had been reprinted, mostly in Dutch. There was a CCG/collectibles shop on one of the roads heading north out of the centre, which had a large collection of singles for Magic: the Gathering. Also, we found a Toys R Us-type place a short drive south, but the selection wasn't too good. There was also an odd little shop dedicated to crosswords and chess just east of the centre.
There are a few other shops listed in the directory, but other than the ones described above they had little of interest.
By the way, I did do other things besides hunt for games shops on my holiday!