Coca Cola is coca cola. It's neither bad nor good. You drink it if its there.
Pepsi is like coca cola but a bit sweeter. Same argument applies.
I hate Mountain Dew so much. It's become the drink that makes nerds look bad. Yet they stil drink it.
Dr. Pepper is not available in Australia, or in my state at least, unless you feel like paying HUGE markups for it i.e. $3.50 for a single can. I remember I used to like it when it was available for a few months or however long it was, but I really can't comment on it since it was years ago.
Root Beer is something I never got the taste of.
I have a geographical tongue so Citrus Soda's (among other things like tomatoes and walnuts) can cause large amounts of discomfort. I also think citrus in general stinks like the aftermath of a walrus scat-orgy. Yeah. That's right. You now have a mental image of hell.
My personal preference is Pepsi, but Coca Cola is just as exchangable. Thats how it works anyway I think. Coca-Cola: The drink you drink, Pepsi: The drink you drink when theres no coke.