They are the almost defacto standard for personal payments online will keep them in the top spot for a long time due to network effects. Without a serious shift in usage, its hard to see that changing any time soon.
As an anecdote, my grandmother passed away last week. Her 86 year old sister back in Germany asked us if we had PayPal this week so she could send flowers for her funeral. It may not be a "hot" company in the US, but its still highly relevant to the vast majority of internet users, even ones that are only just venturing onto the web.
[1] I don't know the actual number as everywhere I've looked suggests between 13% and 15%. I figure less than 20% is a safe bet.