Good on you RH.
I had a quick listen to Mariah Carey's version of the song, posted below.
http://www.youtube.com/watch?v=LoBdt9L_DPA
Just a few things I noticed:
1) Mariah has complete control of her breathing, leading to clearer phrasing, articulation of the words and true pitch.
2) Mariah sings right through to the end of each phrase - completing the phrase if you will. Her pitch at the end of each phrase is always true. That is mainly due to her breath control and using her diaphragm correctly at all times.
3) I'd probably recommend reducing your hand movement in places. It looks a little excessive and detracts from your singing.
4) Mariah sings 'ooh' at the very beginning then changes to 'aah'. - You sing 'aah' at the start. Mariah's 'ooh' is completly in tune. Your 'aah' is not! Perhaps begin with 'ooh' at the opening of the song as this will help with the pitch.
5) Take out the 'yeah' in the introduction.
6) Your pitch tends to be sharp. Developing breath control will help. Do you do singing exercises? Try Conconians - these really help.
7) The ending is meladramatic. Tone it down!
8) Listen to Mariah's version and take notes! She has obviously had extensive singing lessons and vocal training over the years and has developed significant technique.
Regards Jason.