I love black jeans -- I'm always looking to visually slim my bottom half, and great fitting black pants or jeans do that better than almost anything else. I have a pair of black skinnies (Lucky Lolita cut), black full-length flares (Pilcro from Anthro), and an old black pair of Kut skinny/straight leg that fit well but are kind of heavy so I save them for winter.
Oh, and I just remembered I also have black skinnies that I guess qualify as jeans -- they're faux leather front and ponte back.
My most-worn black pants are not denim -- they are Lululemon moto pants. I fear the day they wear out. I love them that much. I love the look of moto jeans, but they usually do not fit my thighs, or the moto detailing is unflattering on my legs. The Lululemon pants have subtle enough detailing that they work.
I find black pants/jeans absolutely indispensable because 1) flattery as I mentioned before, 2) they play with my wardrobe well because I wear lots of black, and 3) they work well for my active casual life -- they don't show dirt and stains so quickly.
I do think that black jeans dress up easier than blue, unless the blue is a uniform very dark wash. That makes black jeans especially versatile.