Remember to make use of the many programmes available online to help you improve your pronunciation and intonation; you can find quite a few in my Delicious Bookmarks or, for individual words, in howjsay.
Imitating the sound of English does not work, either. Here is an example of what I mean: this woman "imitates" the English pronunciation but she thinks she is singing in English (she says so in the video). Her pronunciation is pathetic and only if you know the song (which is the case for plenty of people in the audience), you will know what she means. By the way, this woman, Bulgarian Valentina Hasan, is wrong, this is not English.
This is Mariah Carey´s version of the song - in English.