There absolutely is no best cologne. Everybody's going to swear theirs is the best kept secret in cologne and it's the one that gets them all the compliments from chicks....and every one of them is different. You should get a cologne based on three (maybe four) things:
1. One girls reputedly like
2. One you can stand, or even like
3. One that isn't too popular so that you don't smell like every other guy who wears cologne (scent is tied to memory more than any other sense)
4. Not so important, especially if you're only interested in attracting chicks with it, but one that you could wear for office/school as well as "romantic wear"
Perfumeemporium.com has tons of customer reviews on almost any cologne you could imagine. And there are thousands.
What I have: Chanel Allure (girls fvcking love it), Swiss Army (same, although I think it attracts a somewhat younger crowed), Burberry London (more for colder/evening/romantic, but very nice), Burberry Brit (very interesting, unique, 'warm' scent).
One thing you can do is go to a department store cologne counter and ask for tons of samples, try them out and ask girls how they smell on you.