Bach is great on many counts - I did a visualization (https://github.com/hadley/ggplot2/wiki/Bach-2-Part-Invention...) in R awhile back of a Two-part invention that reflects how well structured his counterpoint is.
I love the fact that so much of Bach's music explores numerical relations and patterns. And I've still not heard of anyone creating a piece as complex as his Musical Offering[3] that sounds at all listenable, let alone sublime. Any person who can compose a 6 part fugue is superhuman IMO.
[1] http://en.wikipedia.org/wiki/Dirk_Gently's_Holistic_Detectiv... [2] http://en.wikipedia.org/wiki/G%C3%B6del,_Escher,_Bach [3] http://en.wikipedia.org/wiki/The_Musical_Offering