To help iPad and iPhone gamers keep track of the really unmissable titles out there, here are six of the most essential iOS games. Some have been out for ages (comparatively). You may have played some already. But if there are any here you've not tried, it's time to get down the App Store.Related StoriesIssues with fingerprint sensor could mean iPhone 5S shortages next monthMicrosoft updates Skype with HD for iPhone and iPad, adds mobile BI app
