Compaq, Asus, Dell, HP all are branded Desktop PC. But I prefer to use clone PC cause if I use them then there is an opportunity to add hardware we need to extend our PC.
Different people used different brands so it depends on there experience. Well dell and hp are the pioneer in this era.
A lot of opinions here, but no-one's asked what do you want the machine to do? It's like asking who makes the best knives, or shoes. Are they ladies shoes or gents? Formal or casual? You get the idea?
HP, Lenovo, ACER are coming up with the best configuration and prices now a days. Recently my friend bought Lenovo PC, it's really cool and having 0 problems in hardware/software wise. Even, the technical support from the manufacturer is too good with immediately/instant response.
The best desktop PC is the one you build on your own. I personally avoid all those branded premade PC-s.