Gateway, dell. My friends have had HP, Asus, gateway, dell, etc... and they are most of the time less reliable than my mac.
My girlfriend has had a MB for 4 years and the only problems with it haven't really been the machine's fault. Spilled drink on the keyboard, etc.
I'm sure there are PCs that fair as well, but in my experience, they're farer and fewer between.
My family has laptops from dell, gateway, and acer. The only problems that I've seen with any of them have been caused by user stupidity. Maybe we're just lucky, but I think most people just treat their laptops very very poorly. The only problem with my old dell is that the power connector has been loose ever since I knocked it a couple feet off a counter onto a hard floor
. The magnetic power connector thing is one of my favorite things about macbooks (that seems to be a fairly common point of failure) but it's really not worth an extra $1000.