The game is called "Halo Chronicles" and is a launch game for Revolution. The concept behind it is that it summarizes the primary events in the Halo story thus far (and fills in the cracks with cutscenes).  It features alot of remade levels, such as the "Silent Cartographer", as well as all new levels that take place before Halo1 and between Halo1 and Halo2.

Features:
-Uses revmote, to aim, to deliver satisfying melee attacks
-Single Player / Co-op campaign includes the best levels from Halo 1 and Halo 2, and also a few new ones, such as the fall of Reach, and the journey back to Earth.
-Multiplayer has similar philosophy: features remade maps based on the most popular ones from the last games (Zanzibar, Blood Gulch) and includes some new ones.
-Overall: 20 Levels for the campaign, 20 maps for multiplayer
-Features one consistent graphical style, so that levels originally made for Halo1, Halo2, and the Revolution exclusive levels all look just as good.
-Similarly, new features, such as being able to board vehicles, are enabled in Halo1, which didn't originally have that capability.
-Free online play

One extra cool feature:  For the "Fall of Reach" level, up to 16 player co-op is enabled through "Nintendo Wifi Connection", since there were multiple Spartans there in the story.