These may not be the 'best' but they're my favorties
In no particular order
Ones I own
Dead space 3 Dev edition - My personal favourite CE
Defiance Ultimate edition - ?62 at launch, can't argue with that for the amount of goodies you get
Bioshock infinite ultimate song bird edition
Assassins Creed 4 Black Chest edition
Dark Souls Limited edition - Had to nominate this one for the art book, I really like it.
James Cameron's Avatar Limited Collector's edition - Was the first CE I bought and I'm a massive fan of the movie so a little biased towards this one.
Borderlands Ultimate Loot Chest edition
Ones I want
Sonic Generations Collectors edition
Halo Reach legendary edition
Dead Space Dev limited edition