Aah. Portal. A game many have been waiting for. And in my opinion, is being near the most perfect game I've ever played. A first person shooter puzzle, with hilarious and memorable quotations, fucking-a voice acting, and yet it contains a good story.
Perhaps a bit short. And perhaps a bit easy. But the advanced maps and challenges make it up. (Least steps and least time being 8 bitches on a bitchboat)
Not to mention how well the "Still Alive" song and "The cake is a lie"-line have pretty much changed the internet from that day forward.
Team Fortress 2 is, perhaps, the most balanced multiplayer game I've played in a while. The only thing bothering me is the weird random "Critical Shit". Kind of points the game more into luck, rather than skill.
Half-Life 2: Episode Two....... ... ......... well... Valve did say it'd be almost twice the length of episode one. Shame. But it certainly kicks the crap out of episode one.
Now, with that said, go watch the Zero Punctuation review on the Orange Box.