Action? Dread? Choose your thrill in this summer's games

The difference between fear and excitement is the difference between anticipation and action, which is illustrated perfectly in Aliens Versus Predator 2 and an expansion pack for it that will be released this summer.

The expansion pack, Aliens Versus Predator 2: Primal Hunt, is an exciting game in which the action never lets up, while Aliens Versus Predator 2, with its long, agonizing periods of deceptive quiet, is utterly terrifying.

Inspired by the movies Aliens and Predator, the series allows players to assume the role of an alien, a predator or a marine. Some people argue about whether Superman could best Batman in battle, but Aliens Versus Predator is more interested in which of these two movie monsters is the better fighter. In the game, of course, the answer is whichever one you are playing.

For me, the least interesting character is the predator, a hunter with a range of James Bondesque gadgets who likes to kill things and take their heads as trophies. I never feel comfortable wearing the skin of a ruthless, amoral killer, although other gamers often say that it's just silly of me. While the alien is equally savage, it's simply trying to survive and escape.

Starting off in the embryo stage as a small, tentacled creature, you must find a lone marine, crawl down his throat and eat your way out of his stomach, then sneak off to a quiet spot where you can grow into adulthood.

Your only weapons are your teeth and tail, but you can climb walls and drop down on unsuspecting marines and tear them to shreds, or lunge at an enemy with blinding speed.

Aliens regain health by eating brains, so while the marine uses health kits to revive himself, your alien health-kit equivalent is a scientist cowering in the corner waiting to be eaten.

While the alien is the most unusual character to play, the marine's adventures are the most terrifying. As the marine, you are slower and more fragile than your enemies. You walk through alien hives and ancient structures in utter terror.

Flayed bodies dangle from the ceiling. Sudden sounds, like the terrifying flapping of huge beetles that flutter in dark tunnels, make you jump. Even though you don't encounter any aliens for most of the first mission, your motion detector beeps periodically, letting you know they are nearby, and by the time one attacks, your nerves are frayed.

The missions are atmospheric and quite disturbing. In one you must seek out a colleague who has been kidnapped by aliens; when you find her, she is affixed to the wall by alien resin with an alien embryo growing inside her. She begs you to kill her.

Such eerie moments are far less common in the expansion pack, Primal Hunt. In Hunt's human missions, you play a sexy female Russian mercenary rather than a marine, and aliens attack you every few steps, slithering along the walls toward you in savage packs, appearing suddenly behind you or climbing straight up cliffs to grab you. In this sense, game play is similar to Aliens Versus Predator 2's multiplayer mode, in which you simply run around killing members of the other species.

Although it can induce an adrenaline rush, Hunt is far less terrifying than the main game because it does not invest time in building fear. You never wonder when the next attack will begin because the attacks never stop.

Players looking for the suspense of Aliens Versus Predator 2 are less likely to find it in Primal Hunt than in Tecmo's Fatal Frame, a ghostly game that is concerned not with violence but with atmospheric terror.