I would say, storage today.
- Harddrive (preferably offline storage with docking station and software to index so you can find what you are looking for).
- Ultrium tape storage
- Blurays and DVDs and CDs
Hard drives are fast, all data there at once, overwrite, delete. Easy to use in docking stations, large space on hard drives. Cheap and portable. Perfect for off line storage.
Ultrium tape storage, not that much space, not that expensive for the tapes, but a big investment for hardware. Long archival life if you do not need access to it and so on. Last is optical, not that much space, where CDs are the best for archiving stuff, hardware is cheap. Probably long archival life. But you can not erase and not cheap. Remember all of the information in my post is with the thought about, price per gigabyte or in relation to that with some other factors.
Optical is best because of price, hardware, archival life and all that. But it is only good for storage of smaller amounts of data. The use of optical should be for stuff you absolutely want to save, personal pictures, movie clips and other important data. You can supplement with USB storage to for temporary storage that you will move over to optical once you are done with editing and all that.
Harddrives are best for mass storage, mostly of stuff you want to save (like me a hoarder of data) but with the option to erase of just to store for as long as I like. If the hard drive breaks down or something happens to it. Bah, not the end of the world. The space hard drives save for me, plus how practical they are, the win out over any other media.
Otherwise buying movies on bluray, dvds, plus music is safe for archival reasons as they will not go bad, you do not burn these movies but it is a pressed disc. As shown here on the forums, people have done error scans of these old discs and they are still good and sound.
The key in my post is simply, store lots of data on hard drives, and buy stuff you really want (blurays dvds) and save important data on gold CDs or something like that.