So what do you think is actually wrong with this piece, sounds OK to me. It may not sound like the original because you probably didn't have a zillion £ recording studio to record it in.
sounds like you did the vocals over the original? Thats why there was a slight echo effect. Maybe worth trying to get hold of an instrumental track of this.
which effects are you using on your voice ,it is very difficult to judge,It sounds to me that at the end of each line either your voice is flat or the effects are making your voice drop on the last note /word of each line .If you put any more music up let me I