Suggestion: Top Played games and Best Solitaire games listings.
On the http://www.vassalengine.org page just under the who is playing section list the 20 most heavily played games and then the 10 Best Solitaire games.
Or the same on http://www.vassalengine.org/wiki/Category:Modules just above the Pages in category "Modules" section.
Update the listings once a year.