Everyone wants to believe the grass is greener and people seem to live in a perpetual fantasy world, just to get through the day these days. Virtual games, virtual lives, the internet has alot to answer for, as wonderful as it is.
I have heard this scenario so many times and some would say well it's not really cheating as they've never met. Recently there was a story about a married man who set up an avator on one of those virtual life websites, where he "married" a woman he'd met there. This had been going on for a while and his real wife divorced him when she found out.