To me it appears people who have ADD or ADHD find games a comfortable fit to provide structure and a sense of control they can't normally experience in open classrooms or even society (things that are already appealing even if you are considered normal).
The farm suggestion is in fact a good one. Routines, repetition, especially coupled with a sense of being rewarded and accomplishing something can prove satisfying to people who can't otherwise control the chaos.
Can games be addictive? Yes, just as much as any object, activity, or idea can be. There is a proven chemical change in the brain. So there is probably a biological addiction as well to some extent. But I doubt it's anywhere near as strong as nicotine or something comperable.
To me the reason games are so compelling to people in need like this, is that they are a perfect fit, and soothing on a level that can't be easily found in day to day lives (like work place grinds or schools). The brain and the environment actually work in unison in ways that put people in a comfort zone. They have... control.
Another reason is single player games provide a place of ownership. In a world where everything is owned by walmartism and foreign countries, your boss, families, children, brothers, sisters, parents, governments, etc... A place or even virtual space that is yours, only yours, and nobody elses, can be important. One of the reasons why DRM is so repugnant, as it destroys the foundation for that belief. All of this is above and beyond escapism and using games to forget.
PS3 resurgance by GOW3 - Check! Mass Effect for PS3 - Check! Diablo 3 for consoles? I say "For sure"!