Of the commonly guzzled brown fizzy drinks from the English speaking world then I would agree Dr Pepper is the no contest, hands down winner with the only exception being it does not mix with orange juice for a muddy puddle quite as well as various colas.
However give me a proper root beet (Dr Pepper was better than the ones I found in more than one chain of US supermarkets -- some had local interest type root beers that did well), sarsaparilla or kvass any time. If we are going for orange, green, clear or red coloured fizzy liquids then there are many other choices there which rank up there with Dr Pepper. If we are allowed a "burns all the way down and out the other side" ginger beer (which I can get in UK supermarkets these days, and cordial type things in more speciality shops) then Dr Pepper only for a bit of variety.