Most fragrances are a blend of individual chemicals and/or essential oils, and as such their scents develop over time. Many perfumes put their showiest, juiciest notes up front, though. So when you spritz one on, what you first encounter isn't the scent as it will be 20 minutes or an hour from now. In fact, a lot of early or top notes are totally different from the full scent that eventually develops and stays on your skin.
When you try a perfume on, don't sniff and decide. Take some time. The best thing to do is to go get lunch, or even give the fragrance all afternoon, and sniff it at intervals to see whether you like where it's going. That way, you'll know that you really love it, not just the first few seconds of it, and you won't encounter any surprises down the line.