I voted for Coca-Cola, I'd prefer it over Pepsi any day. Having said that, I don't think that Pepsi is really bad, it's just... missing something that Coca-Cola has. Here in Germany (and I think in most of Europe too) Coca-Cola is also totally dominating the market. While you can find Pepsi in almost every store where Coca-Cola is available, most (~90%) restaurants and bars only serve Coca-Cola, and not having it would probably earn the waiter some strange glances from the customers because "Cola", "Coke" and "Coca-Cola" are pretty much synonyms here. Actually the only restaurants serving Pepsi here are Burger Kings, and the frequency McDonalds:Burger King is like 5:1 here. Pepsi also sell their products up to 50% cheaper in the same stores, that says quite a lot. And Dr. Pepper? That's totally unheard of here, I think that only large stores which are specialized on beverages even have it. And "root beer"? I don't even know what that is, if I translate it directly into German, then... it sounds very gross to me. Is it some kind of "Malzbier" (lit. "malt beer", it's actually some sort of unfermented beer with <0.5% alc)? At least that has some popularity here, but it is in decline. Another cola which I like is afri-cola, but it's only a niche product. It has 250 mg/l caffeine and less sugar than Coca-Cola, but it's very expensive and only few stores have it, so I drink it rarely.
BTW I've heard several complaints from Americans about Coca-Cola using corn syrup in the States lately. Here, our Coca-Cola uses beet sugar, and I never had the opportunity to try American Coca-Cola. Is there actually a difference? Has someone here already tried both?