I own a Lumia 920 as of last week and have had Windows Phones as my main devices for 2 years now (as well as iphone and a few android devices on the side).
If you want gaming, iPhone is the way to go as long as you don't mind slightly smaller screen.
Where I would recommend a Windows Phone over an iPhone is when it comes social network integration, mail client for work (Exchange) or a keyboard which isn't a spell correcting Nazi. Also the whole interface on Windows Phone is more beautiful than the iPhone's... And Lumia has some wonderful strengths over the iPhone, such as durability, camera and wireless charging.
However when it comes to games and variety (apps in general), iPhone wins easily.







