To the listener who wrote in about the list of games from which he choose to play, I would go against the grain and go with Illusion of Gaia, and strongly recommend AGAINST Halflife2/TheOrangeBox/Portal/etc.. Having played Halflife, Halflife2, all the extra episodes, Portal, and Portal2, I serious want those hours back, or wish I had sunk them into a different game on my own to-do list. I think where Valve was really introducing some new ideas in Halflife, Halflife2 felt boring and empty, because it didn't bring anything new to the table and the old things that it was trying to do again (big scripted events, soldiers with better-than-average AI) it didn't do as well as it used to. The game didn't get interesting until the very last level (and gun), and I think that's why the extra episodes are much better than the actual game. But still, largely forgettable level design. And you know what, I think Valve knows this, which is why they haven't done any work on an Episode 3 or a Halflife 3, despite the cliffhanger ending that the last one finished with, and you don't really hear a lot of people clamoring for more, because the series seems kind of bankrupt on innovation.
I also didn't love Portal, it was just way too easy, which was why you heard of everyone finishing it in about 2 hours. With Portal 2, I felt the only new idea they brought to the table was the gels, but they introduced that very late into the game. I wonder if that was because they thought the initial gameplay model would be too difficult for newcomers to grasp, or if they felt the gel gameplay was too limited in nature to be stretched very far. I think the latter. I also strongly suspect that this is why we will never see a Portal 3 anytime soon-- again, they are out of ideas.