Not all blockchain games are going to be worthwhile to put money into. Though, I can confidently bet that play to earn games in general will grow as time goes on. A great way to get exposure is to diversify. Some people only went into NFT's like NBA Topshot or Cryptoblades that turned out to be unsustainable. Meanwhile a handful seem promising and are sustaining growth like Splinterlands and Axie Infinity.
One option I saw to diversify was the governance token for the fund ran by Yield Guild Games called YGG. The basis of the guild was to own NFT's of various play to earn games and rent them out to members. The owners of the assets share profits with the players that actively participated in making money with the NFT. It is the closest option I saw to resemble an index fund for P2E games. Delegating out NFTs in a rental system for new games can really provide growth to the game too. Splinterlands is one of the games YGG recently announced to take part in even though there is a standalone rental system anyway.
The only downsides I saw about the YGG token was being based on the Ethereum blockchain, which seems too gas heavy right now. The major issue though was the execution of the token launch, it sold out to less than 40 holders. A small ownership base does not seem fair for a governance based token on P2E funds.
Right now patience is key too, cause there will be other index related options to follow in the future with how the field is developing. In the mean time having a set of guidelines to follow and sticking to a handful of P2E games may provide a substantial return. Aside from measuring money metrics, simply having fun and improving will surely provide a good ROI.