It is all a numbers game ...
Regardless of the platform they're developing for 90% of third party games suck and only about 2% are really amazing. If your sales are poor and you only have 50 third party games published on your platform in a year you will only have 5 good third party games released in that year and 1 amazing third party game; on the other hand if your platform is popular and you have 250 third party games published in a year you will have 25 good third party games released in a year and 5 amazing games.