My opinion:
Is it wrong? No. Much like violence, sex, and absolutely everything else, swearing in games is not wrong. It's impossible for a thing in video games to be "wrong" because games are fiction and therefor not real. I honestly don't believe that it is possible at present for a game to be "wrong".
Is it good? Not necessarily. Swearing is a tool to convey emotion. When used properly, it adds a great deal to the experience. The problem is that, much like every other tool since fire, humans use it incorrectly an awful lot. See, game developers see "swearing is a tool to make your dialog more gritty and real, and adds impact when used sparingly." and instead read it as "swaring makes any poorly written dialog instantly gritty and real, and adds impact when used like a fire hose". Of course this gripe applies to movies, rap music, and even private citizens in regular conversation.
TL;DR: Swearing can add to a game if you do it right. Most developers do not.