Call of Duty games have always had a very cinematic approach, and World at War is no exception. From groggily coming to as a POW in a Japanese outpost to tearing down the Nazi Swastika and replacing it with the Red Army banner amidst gunfire, the game supplies interesting characters amidst a powerful backdrop, and like its predecessors manages to do it all (and do it well) through a first-person viewpoint. The Russian campaign is more of a success than its American counterpart in this regard, with a particularly gripping mission involving two Soviet snipers sneaking through occupied Stalingrad to hunt down and assassinate the local Nazi commander an exceptionally outstanding portion of the game.
Some of the most effective moments of storytelling are the ones that ultimately have no consequence on the game whatsoever: in the beginning, Pvt. Petrenko lies half-dead amongst other dying Russian soldiers, and a patrolling Nazi dispassionately pumps a few rounds into his comrades to finish them off. Later, you (as Petrenko) are given the choice to execute mortally wounded German soldiers or to let them bleed out and die. Your choice does not affect the game in any way; even so it's still one of the moments in World of War that gamers are likely to remember after the fact.
World at War uses a slightly enhanced version of COD4's graphics engine - a smart move, since Modern Warfare looked great. Due to the setting, the events of World at War are on a larger and more traditionally epic scale than its predecessor, and sections like the final storming of the Reichstag really do look fantastic. It's during the urban warfare missions of the Russian campaign where the visual design of the game is at its absolute finest. The American campaign takes place entirely on a handful of islands, and with the exception of the final mission assaulting a Japanese castle, the lush tropical scenery tends to blend together in one's memory.
When it comes down to it, Call of Duty: World at War is essentially Call of Duty 4, only set in World War II. If you liked COD4, there's a pretty good chance you'll like World at War. If you didn't ... well, this game probably isn't for you. It's not quite as good as its predecessor - vehicle combat isn't as smoothly integrated into the game as it might have been and feels more like a distraction than anything else and the missions are usually on the shorter side, to name a couple of letdowns - but it's a shining example of how to do World War II well even when most of us are already sick of it.
Bottom Line: It's COD4 set in World War II. Awesome, cinematic visuals with a great sense of context and smooth tried-and-true gameplay, though short levels, tacked-on vehicular play and a buggy PC version keep it from being as good as its predecessor. Still, WW2 games don't come much better than this.
Recommendation: If you liked COD4, pick it up. If you didn't, avoid it. If you really, really love killing Nazis, you could do a whole lot worse than World at War.
John Funk thinks Nazi zombies should be a requisite enemy in every videogame ever made.