> Most people aren't evolved to resist serious strains of flu, but when an epidemic happens the next generation will be those who were.

It's true because diseases kill unprepared and leave only the (more-less) adapted. So far neither obesity nor computer games were successful in killing people on the mass scale fast enough. Also, we're actively engineering the computer games to be as immersing as possible. If a 'resistant generation' pops up, it'll probably at some point engineer addicting games for itself.