I agree with the above.
What games actually do, imho, is give you sheer, unadulterated happiness.
How? The reason is simple. A psychologist called Mihaly Czikzhentmihalyi (sp?) discovered (I think in the 60s and 70s) through extensive questionnaires with statistically quite large samples, the secret of ordinary human happiness, and it’s laughably simple - basically, if you go through life setting measurable goals that are just outside your comfort zone to attain, and then attain those goals, and then move on to pick a new, slightly higher-level goal, etc., etc., etc., you will be happy.
It’s exactly this progression of increasing powers and ever-increasingly-difficult goals that games give you in a miniature, abstract form, and that make them so addictive - little jags of happiness as you set and attain mini-goals, constantly excelling yourself in skill, the attainment of lewt, the discovery of new stuff, etc., etc.
Of course, theoretically, we should all be getting that kind of happiness in real life, through our careers, family, etc., and most of us probably do, but sometimes life isn’t so forthcoming, things are difficult, and it’s nice to have a happiness-producing substitute.
But of course, addiction is an ever-present possibility with videogames. I find myself always having to keep a weather eye for the symptoms. Avoidance of real life stuff, avoidance of social life, irritability when forced to not play, etc., I recognise I’ve had these at times. But as someone pointed out above, I used to get it with books and comics too, when I was a child. (In most fiction books, of course we live the “hero’s progress” vicariously.)
For me, addiction gets particularly heavy with MMOs, much heavier than with single player games. With a single player game, I might get addicted to it for a couple of days at the most. With an MMO in the first flush of love, it’s a several-week addiction in the course of which I almost can’t be bothered doing anything else at all. This has happened to me twice now, 3 years ago with City of Heroes, and at the moment with LOTRO.
It’s a sweet, and pretty harmless addiction, but I do recognise it is an addiction, and that it’s a possible danger.
The upside is that you do eventually get bored with any given game at some point - the craving stops one day, quite of its own accord. Not so with drugs - the craving continues until you actually stop taking the drug.
All this with the caveat that people can vary tremendously.