[Platfus]

The Explorer edition is actually pretty neat. Its actually a wooden box so when mine arrives I will take some pics.

On the other hand; best PC CE is probably the Star Wars the old republic. It was really great ce, even the game maybe killed it little bit. As fan of star wars I'd really love to have that one. For Wii CE I find the best one Epic Mickey CE NTSC or Epic Mickey 2 Power of two german edition. Not really into japanese CEs games so dont know. They are not that common in czech republic. Best european CE is probably the Risen 2 keg edition for me. Could be counted as PC as well. After this one, I'd say Assassins Creed Brotherhood Codex edition and Darksiders II uk/ french collectors edition. That CE is kinda beatiful and I'd really love to have it.
When it comes to steelbooks I cant really tell so I will say my personal favourites: Uncharted 3 Belgian stickerbook, Uncharted 3 Italian steelbook, Darksiders II shiny steelbook and probably diablo III steelbook