Keep in mind that any list of games at this point is:

1. Likely to be inaccurate or incomplete.
2. Only a first round.

Provided that the beta goes well, we are likely to see MANY other games.

I can't help but notice that there are a few games in that list that use game engines found in multiple games. For instance, once L4D2 is working, portal, portal 2 and quite a few other games could be ported with comparatively little work.