I like Alex Ross and think the works he's involved with that I've got; Kingdom Come, the Earth X trilogy, and Justice, are all very entertaining (though, it is a bit early for Justice). As for his art - I like it because not only is it well crafted and competent, but it is distinctive and honest (not 'oooh, they look real' honest, but they feel true to who they represent).
It seems to me most criticisms about his work seems to be about his personality, while any criticisms of his art are subjective and buried underneath snide remarks.
I don't really have much opinion on Alex Ross as a man, and I don't pick up comics that he just did the cover for (only Adam Hughes does it for me), but in my opinion, Kingdom Come was an intelligent story about mass production and the entertainment industry, and the Earth X trilogy was a powerful spiritual journey into the meaning of life. If only 0.05% comics are important, Alex Ross has done his fair share.