I couldn't agree with you more. With all the soundtracks, they do seem, to use a description that has been given, "blend together" and all tend to sound alike at first/second/third listen. But like trent has said, good music will reward you after time.
I've been giving each soundtrack about a two-week listening time-frame over the past month or so ( I have an hour drive to and from work) so I have been able to really give it a good listen. Each soundtrack is so distinct and rewarding in its own way.