I don't have the exact specs: The Collectors editon comes with extras like a usb2 stick, a statue, blu-ray or dvd with info about how the game was made, a music cd I think.
The usb stick has one of these bundles on it, I can't confirm since I've read mixed reviews/product specs: Diablo2 and it's expansion pack, or Diablo1 and 2. Not sure if Diablo 1 works on new OS's if it's there.
What do you want and how much do you play? Maybe Diablo 3 and it's probably future expansion packs are the right choice for you. I see the regular price of D3 and the price for Diablo2 with the expansion pack, a guide and/or something else, and it's not bad.
Someone would probably put the interviews/how they made it online. Not encouraging anything sketchy, just a comment. But Blizzard probably has their clips online or will for their promotion and to discuss the game. Sometimes you need to look in the folder trees of installs and you can enjoy the midi or sound files that install with the game. Other times they are locked on the disc.
Not sure if I'll buy the game. But I do video and photo editing, like art, draw, make music and listen to it, don't have Diablo2 (or 1 anymore), etc. So that collectors edition could work for me. Or Diablo2 with expansion and guide/other thing and Diablo 3 by itself.