The Orange box is quite possibly the best value in gaming today.
Half Life 2, what can I say about it? Its been called one of the best games ever made for a few years now. Compared to the Xbox version graphics, the 360's graphics are upped a lot to the point of a high end PC. The gameplay is true to the PC version, just some players may not be as used to it with the controller instead of the keyboard and mouse. The newest part to the series is Episode 2 which has the best graphics of all three parts and the best facial animations of all three. Next is Portal, some may find it slow but if you're a big fan of puzzles and want to take the puzzles they gave you in Half Life 2 to the next level, this game is for you. You basically take what part of the hype of Prey was and a gravity gun, and solve puzzles by trying to get to the end of each level with the use of two portals. At some points, this is one of the trippiest games ever. You can get so turned around by going upside down left to right and up and down with all the possible portal combinations. There isn't a whole lot of variety, but if you like puzzle games and want an interesting first person twist to it, you will find Portal to be an amazingly fun game.
Last is Team Fortress 2, the sequel to Team Fortress Classic, one of the original Half Life mods. You have pretty much the same concept with new levels and some abilities, but this time they're using an extremely modified version of the Source engine to have a hilariously cartoony cell shaded imagery. Honestly thats why I love the game so much, the art direction of the game is one of the best this years and rivals my love for Eternal Sonata. This is the generation where Cellshading can really shine with brilliance. As far as the controls go, it translates well to the 360's controller pad. Though it would be a lot better with a keyboard and mouse, but the upside is that everyone is going to be using a controller so no one will have an advantage over you.
Over all, the Orange Box is just great. You cant argue against Half Life 2 and Team Fortress (Portal can be an acquired taste) and the value of all this for just $60. If you are a FPS fan and don't have a gaming PC, just buy The Orange Box, simple as that.