What lasts longer: Data stored on non-volatile flash RAM (USB stick or SD cards?), optical media (CD, DVD, or Blu-Ray?), or magnetic disk (floppies, hard drives?) My gut tells me optical media, but I'm not sure.

Furthermore, which of those digital media would be most suitable for long-term data storage where environmental issues are unknown, such as low/high temperature or humidity?

For example, what digital media could be stored in a basement, attic, or time capsule, and be expected to survive a reasonably long time? e.g. a lifetime, and then some.

Update: Looks like optical media and magnetic tape each have one vote below. Does anybody else have an opinion or know of a study comparing the two?