VGA is analogue. You cannot run digital through it. Component, HDMI, and DVI will work for High Definition. As for the BluRay, really all depends on the player. I personally use my PS3.
edit: As far as the 120hz goes, I dont know why it would matter what source the digital signal is coming from. You should still get that refresh rate. But I am not 100% positive on that.
edit: As far as the 120hz goes, I dont know why it would matter what source the digital signal is coming from. You should still get that refresh rate. But I am not 100% positive on that.