In most of Europe, kissing each other on the cheek in informal settings is also perfectly normal, but usually not between men. Where I'm from (Netherlands) three kisses on opposing cheeks is more or less the standard greeting if at least one girl/woman is involved, but only after you get to know each other a little better. In other European countries, 3 kisses is weird but 1 is normal. I've never been anywhere in Europe where hugging is considered a normal way of greeting, except among close friends and relatives, and usually only in special situations (haven't seen each other in a very long time, or meeting under difficult circumstances). When I visit the US, the first time someone tries to hug me still keeps surprising me...

So yeah, greeting seems to be a pretty diverse and complicated cultural phenomenon ;-)