There are a number of things which affect ping: It depends alot on the route your packets take getting to the other computer. Routing occurs depending on the algorithm used by the routers - but the idea is to generally take the shortest distance and/or the least congested route. Sometimes that means the route is longer in terms of miles. It may also depend on how busy the server is that you are connected to etc. I'll bet the infrastructure in your area affects it too.
Dial up users often get higher ping latencies, as do I - typically between 500 and 800 milliseconds, and sometime higher. This seems to occur whether I connect someone in the same city, several states away or overseas in the UK or Europe. High speed users generally seem to get ping rates an order of a magnitude lower. I suppose this is simply a function of speed - but they also have to do router hops and all that jazz so I'm not sure why they are so much lower.