I'm tempted to say that this episode really didn't have all that much substance to it, mostly because it took an idea that felt somewhat dull (Penny learning to play a video game that Sheldon likes) and also feels somewhat overused (I feel as if I've seen this scenario in several different shows). However, the episode ended up taking the show's best character (Sheldon) and using him to bring out the best in Penny, a character I've felt distant from up until this point.
I think the reason it was so good is that the relationship between Sheldon and Penny is actually funnier and more believable than the one between Leonard and Penny. Leonard and Penny seem so distant that it's not even fun to watch them try to get together. I really hope they don't in the end and instead find more interesting things for them to do.
However, back to Penny and Sheldon; they have a great way of having a back and forth relationship, and she's the perfect understanding person to comprehend how socially inept he is. I also thought that the "Age of Conan" plot was pretty great, as it was a perfect symbol of the stuff that was going on in Penny's love life at the time.
Definitely the best of Season 2 up until this point.