Thanks for peoples understanding.
It's a sad fact that games like Mutant Storm do not perform well on the App Store - the race to the bottom saw to that. The biggest problem is players move onto the next games very quickly because they can get something for 99c or free, play for a few days then move onto the new releases and keep doing this in an endless cycle. This really kills the word and mouth of recommendations that players give to each other. Games just do not get settled in the chart positions.
The App Store is just a casual market - most hardcore gamers are console users and tend to ignore iOS completely.
Anyway, I'm going to have some fun and do some nice 2d games for a change - something I've been meaning to do for the last year or so.