Having lugged around those gigantic 21" CRTs to LANs as a kid, the concept of being able to carry fully-fledged PC games like Duke Nukem and XCOM in my pocket would have blown my mind. But while they're some of the most recognisable games, there are plenty of other classics from all platforms you can grab on iOS and Android right now - and you don't have to deal with a compromised experience or dodgy controls either.