I understand it might be frustrating, but at the end of the day you get what you pay for. The 620 is not meant to be a top Windows Phone, it's meant to be a low to mid range device and in those parameters it's fantastic value.
The OS is lovely, the phone feels nice in the hand, and the range of apps/games that don't run on it aren't life changing. I have a WP 7 and bought the 620 so I could get apps like UK TV streaming apps, and WP 8 exclusive games like Where's My Water. It being a low end phone I don't expect to be able to run Modern Combat or Spider-Man - buying it I knew it won't unless developers lower the requirement. They did this with Asphalt 7 so this is possible, but if you are an avid gamer then you shouldn't really go with a low end device. If you lower expectations, the 620 is great, including for gaming.