Doesn't have to be 5, it can be 10, 3, or just one. I know I am true to several name brands, and would buy any of their guns in a hear beat.
1) F.N. & Browning
3) Heckler & Koch
These three have to be separated..... Colt and F.N./Browning are really tied, but if I had to choose just one it would be F.N..., The Browning name matches the artsy Colt guns, and the refined military efficiency of F.N, coupled with their large catalogue and range of weapons edges out Colt. H&K is to expensive, and doesn't offer a great variety.
A lot of people want to hate, but I LOVE the 92fs especially, along with their carbine line, the neos, nano, and PX4. However they lack the power factor that modern guns need. (No bad a** military rifles such as AR-15, G3, or Scar-16s)
5) Smith & Wesson
They are really nice, and in the same category as Colt, F.N, and Browning, but just aren't as great. They are very very VERY good, but are not one of the GREATS in my book.