Half Life: Episode 1:
Starts off where the first game ended, you are just about getting a task from G-man when vortigauns saves you and Alyx. Your task is to capture secret documents from combines in the main building and then get out off there. Soon you end up playing for a very long time in dark tunnels, which aren't so fun when there is new combine suicide zombies, it suited better in doom 3.
There really isn't much new to see in episode 1, and it's very short. Played trough in 4-5hours. But it has it's moments and is better than average fps
Half Life: Episode 2:
Starts after the train wreck where ep 1 ended. This episode plays in beautiful outside scenes and are much more enjoyable to play than ep1, and with new interesting character's and good wrote plot with a very funny and challenging battle at end.