A friend gave me a link to
http://inselkampf.com because she recalled me talking about browser games when she heard of it.
Inselkampf has no tutorial, one non-obvious help page, almost no graphics, no layout, no integrated forum or chat, maybe no inducements to interact with other players, gameplay entirely based on
farming, and (what I think is killer) the first thing you do in the game is click a tiny icon to start an 80 minute build - with
nothing to do until that completes.
Poking around in the rankings, it has 31,000 signups and 99.97% of the accounts have a score of 0, implying they never even started the first building. (Maybe they did and the game allows buildings to be destroyed; either way those accounts are abandoned.)
Seeing dozens of games like this with tens of thousands of signups and almost no players are why I thought there must be a market for a good game.