I always go with Intel and Nvidia myself.
BUT the landscape could change in a couple of years. AMD made the best chip PERIOD back in the days of the Athlon/Athlon XP.
But Intel took the lead and AMD has not been able to keep up. Who knows though, they could have a killer chip in the works and we could all be shocked!
ATI (before they were bought up by and renamed to AMD) even held the lead for a while. They had a better product, better drivers, better everything... but lately it's been Nvidia all the way.