Man, you can actually earn money from almost any game. Let's take per example cs:go, you can easily sell the skins or even sell the lootboxes you get from valve. Yeah those lootboxes don't cost that much yet can make some poket money. But if you only want the lumens i don't really think that there is such a game, only if you are not a gambler as nowadays as i understood the crytpo gambling is only getting more popular. And a big advantage for the crypto casinos is the fact that some casinos are not covered by gamstop, so it is really easy to earn the lumens or any other kind of crypto currency, as crypto gambling is not limited to only one currency. As i understood, lately the altcoins are the ones specific for the gambling.