I do not look at the ranking when someone participant announces the project on the Bitcointalk forum. projects that steal the public's attention are projects with the latest innovations in cryptocurrency where the concepts that are brought are still unfamiliar in cryptocurrency.
Indeed the purpose of the project itself is much more important because thats how we can see the uses and advantage of supporting the product.
On the other side a reputed member of this forum who will manage the bounty or the one announcing the project is sometimes an indication that it is legit (though not all). Because a legendary member is trusted compared to newly created accounts.