wat is the big deal about orange box?

360 games i plan on getting the rest of this year:assasins creed, mass effect, madden 08, pgr4, and dead rising. i fail 2 c orange box on the list. wat is the big deal?

For those who have never played Half-Life 2, its an amazing package. Personally, I only played through the first Half-Life 2, not the expansions... so this was still a great deal for me, plus portal is cool and TF2 is really alot of fun. Its a great deal.