I would suggest:
"Raiders of the Hawaiian Box" (Not to toot my own horn, but, I really think that some more THAC brickfilms should be included, as, it's one thing to see a great brickfilm, but, another to see one that was made all within 24 hours. Not to say that my THAC film is good... at all... because it's not)
Doug Vandegrift's "Pirates" and "America: Outlawed." (I don't know how much space you'll have on the discs, or how many discs would come in one collection, but, I think that if I was making a list of "greatest brickfilms to represent the community" those would definitely be on there!
I'd also want to suggest "Alex and Derrek: 5 Years Later." But, to understand that film, you'd have to have some of Nathan's earlier Alex and Derrek brickfilms too.
Mindgame's "Hypothetical Possibilities," Robinson Wood's "Grace," and, of course the classics, "Robota" and "The Gauntlet" would also be some of my considerations. (Though most were made in the times of Brickfilms.com, not BiM...)