I am wondering if someone from GOG can tell us how the list of popular games on the front page is ordered? I find the constant presence of the Witcher on the very top spots surprising. Even now, after everyone who's bought Divinity:OS got the Enhanced Edition auto bought for free, that game still shows up below the various Witchers. Are the three Witcher games currently on the top locked there? If so, why not mark them as such?

Games are ordered according to their sales. The Witcher 3 has not been permanently on the top spots. It's just that the first expansion came out recently, so more people are buying it.

As far as I know the list doesn't show the games that sold most units, but the games that made the most money during a certain period of time. Don't know exactly what this period of time exactly is. One week? Three days? 48 hours?

Because of that there are usually some expensive games at the top, followed by some games from the recent promos. And it's quite logical that The Witcher has been (and still is) on the top of that list. The game cost around $65 and an average game from a weekend promo has to sell more than 20 units to get the same revenue than one full price copy of the latest Witcher game.

That's a good explanation, which I had not heard before.

Which immediately gives me an idea on how to make Witcher 3 even more popular: make it even more expensive.

... and then put it on a promo!

I can see the headlines:
"A once in a lifetime opportunity to buy The Witcher 3 at +50%. Get the most popular edition of The Witcher 3 yet and be the most popular guy or gal among your friends"

As I've said when this subject has come up in the past, that would be a terribly silly way of doing things -- units sold is pretty much the standard for these sorts of things. (Not that GOG always does things the sensible way....) Obviously they are not counting titles that are given away for free in their units sold (if they did, then games that are permanently free, or which are given in time- or unit-limited giveaways, would show up on that list, and I don't recall this happening), but that doesn't automatically mean that they're ranking by money grossed for all titles. Frankly, I would find it easier to believe they were just artificially keeping The Witcher 3 and its expansion packages at or near the top of the chart artificially as a means of promotion -- and, as popular as the game is, I seriously doubt they have any need to do this.

Units sold does seem to be the case if you sort the Games Catalog by popular. The front page though seems to be by money made.
Do remember to check it on the next high profile release, and compare the place the new game is in the front page to the place it is in the catalog, comparing it to the other entries in both lists.

The bestseller list in the games section (which is for the last year) is for units sold and only the list on the frontpage is about revenue. I'm pretty sure about it, because I've monitored releases from the same day several time. Even if the more expensive game is below the cheaper game in the games section, it's almost always higher in the list on the frontpage. Can't find another explanation for that.

And for GOG it makes indeed sense. The more expensive games are more profitable for them, so it's good to give them a lot of exposure on the front page. And a high rank in the bastseller list implicates that it's a good and very popular game, so it's more likely that people will buy it.

My reading of it is that it is based on the base price, not any discounted prices. So expensive games that see 80-90% discounts on sales (that move a lot of units) will still wind up closer to the top of the list.

More simply, I think it's base price x units sold, rather than total receipts (only for the amount of time that is used for that list).

But one of the blues has stated before that the Bestselling sort order on the Games catalog page is long term -- ≈ the last year; whereas the Popular tab on the front page is obviously operating off a much shorter time frame. It's totally possible --common, even -- for Title A to have sold way more units in the long term than Title B has, but Title B to have sold more units in the last day/few hours/whatever time frame that tab measures.

I feel like I've had this conversation before (likely even with you!), so I'll say no more here. =)

You have to look at Title A and Title B when they are released on the same day with different prices. After some hours they will have different position on the long term list, but the more expensive game will almost always be higher ranked on the frontpage. That wouldn't be possible if both lists are about units sold.

Check the front page. Galak-z is in position 20, and it was released on October 29th. Dungeons & Dragons: Krynn Series is in position 21, and it was released on October 27th.
Krynn Series is in page 22 of the catalog, Galak-z is in page 25. Krynn has sold more copies than Galak-z, but it's lower in the front page ranking.