In a perfect world, all of them. But that will never happen.
A reasonable but still far-fetched goal would be
all boxed games.
Unfortunately, that's far-fetched because Mike sees VASSAL et all as a sales driver, not a basic requirement, and is therefore loathe to allow modules for games that are not in stock.
Trimming our goals even further, then, I'm hoping we can do Elsenborn, Cassino '44 with campaign support, and all new boxed games.
Let Mike know you care. That's the best thing anyone can do besides making the modules themselves!