The best deal in gaming. Period.
A testament to Half-Life 2's quality at its launch, this six year old game still holds up incredibly well and doesn't look one pixel out of place amongst the fleet of high-profile first-person shooters on the Xbox 360. While the graphics aren't nearly as dazzling as Call of Duty 4, the intricate physics engine and the quality of the storytelling make Half-Life 2 as deep and fulfilling a game as you'll find. As a relatively young gaming classic, it merits the purchase price alone.
Playing the game again in 2010 gave me a new perspective on the gaming industry--while graphics have gotten better, budgets have gotten bigger, and sales have risen to the stratosphere, game quality seemingly plateaued in 2004, the year of Far Cry, Halo 2, and Half-Life 2. This game set the bar for character models, storytelling, interactivity, and player immersion, and that bar doesn't seem to have moved one bit. While we like to believe that there's something next-generation about today's games, this summit has been inhabited since as far back as 2004, a full year before the release of the Xbox 360 and nearly two years before the PS3.
The same high production values of Half-Life 2 only get better with Episode One and Episode Two, with slight graphical improvements but also more emotive characters and one of the best science fiction storylines in modern gaming. Half-Life is a weave of complicated politics, mysterious figures, and unnamed benefactors that doesn't seem to have a black and white--you know who your enemies are but you don't know who you're fighting, and the game leaves so much mystery that it's easy to get lost wondering about it. This is a far cry of the black and white storylines of games like Call of Duty 4 and Halo, where your opponents are definitively evil and impossible to sympathize for.
Portal is the surprise hit of the package that has left a huge mark on gaming culture. As often as I see forum members quote "All your base are belong to us" I also see references to the cake being a lie, or people bursting randomly into the song at the ending credits, easily the funniest ending to a game EVER.
Portal, while short, is a completely unexplored territory of puzzle solving that showcases the continued originality of Valve, which after nearly 15 years of high profile industry status, is on the forefront of innovation. The game is a blast to move through and the tongue-in-cheek humor never gets dry.
And then there's Team Fortress 2, the sequel to an original Half-Life mod, which was originally a Quake mod. How exactly Valve arrived at the cartoonish 60s spy theme I don't know but I don't think it gets much better than this--the class based competition is so varied and unique that there is a nearly infinite amount of replayability to this game.
I sunk 30 hours into TF2 within the first couple weeks of owning the game. It's an engrossing experience, and you can always try something new. The amount of replayability is incredible for a game that only sports a handful of maps and only 16 players.
The only downside is that the community of players is pretty small this late in the game's lifecycle, and while other, older games like Halo 3 and COD4 have stayed alive, Team Fortress 2 is seemingly forgotten by Valve. Licensing and quality control issues with Microsoft have prevented Valve from releasing updates with the same frequency as the PC version, and also free of charge. The 360 version is nearly 3 years behind the PC version in terms of updates and that doesn't look to change anytime soon. With that said, there is still enough players to join full games and have a blast doing so. You might even make some friends since you're likely to see the same players time and time again.
The sheer brilliance of The Orange Box is that each of these games individually would merit the bargain bin price of $20, but instead you get all five. In an age where shooters are slowly creeping below the 5-hour campaign threshold, you can easily squeeze over 100 hours out of this one disc, making this easily the best gaming value money can buy.