It also mentions something interesting about extra content with the game:
Classic content - Ultimate DOOM, DOOM II, and all new Master Levels for
DOOM II classic content, playable in single player, split-screen 2-4 player
co-op and deathmatch modes
That's all well and good I guess, however having The Ultimate Doom and Doom II encluded kind of negates some of the limited-ness of the Doom 3: Limited Collector's Edition; seeing as how these additions were its biggest attraction over the regular retail version.
The Master Levels for Doom II was a map pack for the game back in the day, somewhat of an expansion set; though I don't think it was considered an official part of the original Doom trilogy as you can't even find it on id's web site. If I recall correctly, it wasn't developed by id Software, rather it was a collection of maps fans created pulled off the internet. I never played it, but I recall reading there were over 90 maps. Should be fun, though I was really hoping for Final Doom, the final title of the original Doom trilogy. While nothing new or inovative, Final Doom's first episode, Evilution, had exceptional level design. It's second half, The Plutonia Experiment, sucked balls.
I'll leave you with an old but great screen shot from PC Doom 3.