source?

Indeed, one of my first games was Small arms and Ecoo the Dolphin =p.  I think the next one I got was Geometry wars but I started to love XBLA when I touched Castle Crashers for the first time :).

According to MonstaMack who looked at the Fez leaderboards a week ago Fez was at ~90k.
American Nightmare had 55k at the end of April but Microsoft said that due to the way they implemented the leaderboard, sales are about double.

http://gamrconnect.vgchartz.com/post.php?id=4556314
http://gamrconnect.vgchartz.com/post.php?id=4524486

Surely a bit disappointing numbers (especially that I am Alive did much better than American Nightmare)

The Walking Dead also had a great opening:
http://www.joystiq.com/2012/05/11/the-walking-dead-tops-xbla-activity/

those are some pethetic numbers for Alan Wake, surely they can't be correct, only ~100k? I hope it does better on Steam. I really like Alan Wake and I though the reception of American Nightmare was pretty positive.

Considering what Fez is those numbers are quite good. I wonder if it will have Braid like legs, that game only did arround 55k in it's first few weeks, but went on to sell very well.

~110k in the first 6 weeks. By now... 150k maybe ? We'll see.
Again I am Alive did 150k in 4 weeks, so Alan Wake certainly was disappointing in comparison.
Without having played it, I think the problem is that it focussed too much on combat and not as much on the narrative. Basically the exact opposite of what made Alan Wake so great. The 2 DLCs were already full of combat driven gameplay, so I can understand that this gets treated more like a 3rd DLC.

I'd assume Fez and AW would have legs in the long term. I enjoyed the demos for both, but the problem is they're both very good games competing with many other good games as well as a pile of must-have games. At this stage the XBLA library is massive and while I think MS has done a decent job to keep the chaff down, that just means that the majority of games are good to very good, so it takes an exceptional game to stand out.

i would say its more about the games, you do get some neat little games on XBLA

The problem with the leaderboards is a lot of the games you have to scroll down all the way to the bottom to see how many people are listed. Some games have a total user amount while others don't. Alan Wake was pretty low but It hasn't been out that long. Give it some time and a good sale and I'm sure it will be higher.

With Alan Wake, what do the leaderboards consist of?  The campaign or arcade mode (or both?)?  I have Alan Wake but I haven't given arcade mode a chance, yet.  If I don't count (and I don't know.  Maybe I do count.) maybe there are others that just didn't give that side mode a shot. 

From Gamasutra:

"[Update: Microsoft representitives have contacted me regarding the Alan Wake: American Nightmare numbers. While not being specific, they suggested that the sales were roughly double that than we have suggested. This would be thanks to the game only adding up the numbers once a player has completed that chapter -- it's not instantaneous. Sorry for any confusion!]"