Marvel Minimates are the only block figures I collect. I picked up the first series of Star Trek figures, but when I heard about the scale change from 3" to 2" for Marvel, I decided to stick with Marvel. (Trek looks dead in the water anyway.)
I keep hearing DC Minimates are in the works. Nothing's cast in stone, but if it happens, I hope like heck they're offered in the same scale as Marvel. These things are addictive.