Surpassing Half-Life 2 with team based gameplay, better enemy AI, and updated graphics, Episode One lacks new additions.
The gameplay is actually better than the original Half-Life 2, since you (as Gordon Freeman) spend almost the entirety of the game with one of the fan favorites of Half-Life 2, Alyx Vance, a tough, automatic pistol wielding character who through the Source engine's amazing face poser and equally amazing voice acting is very 3 dimensional in her portrayal. Her interesting and entertaining comments run the gamut from lame jokes to horror filled comments about stalkers, and you never feel alone as you might have in some of Half-Life 2's long solo sequences.
Enemies have also been improved in Episode One. Combine soldiers make better use of cover than previously and Antlions come out of burrows that can only be plugged by covering then with wrecked cars. The only reason gameplay gets a 9 instead of a 10 is the lack of new enemies or weapons. The only new enemy is the Combine zombie, or as Alyx named it, the "Zombine." Though a terrifying opponent which can take as many as four direct shotgun blasts to kill at the normal setting, and made even more terrifying in the fact that the Zombines have a habit of running at you full speed with an armed grenade, the lack of any other new enemies and especially weapons restricts your tactics to the same ones used in Half-Life 2.
The graphics for Episode One have also been given slight additions. Though I can not attest to how good the graphics can look, since I have a very bad graphics card, I can state that they are the best I have seen on my computer.
With the return of the entire cast of characters from the original Half-Life 2 comes the voice actors who brought them to life. The voice acting and game sounds are just as great as Half-Life 2, but the music is still just as weak, showing up every once in a while and not really doing anything for the game.
I give the game a reviewer’s tilt of 10 since I feel that Valve has done a great thing for the Half-Life saga by moving to episodic content. While it took six years for Half-Life 2 to come out after the original Half-Life, and 16 months for Episode One after that, Episode Two is expected in only 6 months and Episode Three in a year. With shorter games and thus shorter development times, the long gap between the famous cliffhanger endings the Half-Life series is known for can be shortened a little bit, not to mention the graphics of the Source engine can be constantly updated.
Once again, Half-Life 2: Episode One is a worthy successor to Half-Life 2 and I am looking forward to Episode Two, especially after the teaser provided at the end of the game.