The graphics, sound, and physics in Pariah are better than in Doom 3, and most importantly, the gameplay is also very satisfying. The game is an action-packed blast from start to finish. Each and every gunshot from your weapon, whether it's a bulldog (machinegun-type gun), a plasma gun, a frag rifle (shotgun-type gun), or a sniper rifle, is just so utterly satisfying, thanks to realistic weapon sounds and appropriately rough gamepad vibration effects. You can even upgrade your already excellent weaponry by applying "weapon energy cores" to them. These upgrades improve your guns in ways such as increasing the rate of fire, increasing accuracy, increasing strength of the ammunition, you name it. Later on in the game, these weapon upgrades greatly increase your chance of survival.
There are also lots of enemies to unleash that awesome firepower against, and their AI does not disappoint. In addition to shooting you (of course -- how else would they be your enemy?), they constantly circle-strafe, run like hell, and find cover in an attempt to avoid your gunshots. Don't be surprised if you miss a few of your gunshots trying to take these enemies down -- they are certainly great enemy soldiers, but are very possible to take down.
A unique and well-presented storyline fuels the single-player game. Rather than the same old generic "aliens invade the earth and you are a tough guy who must stop them" plot we get in most first-person shooters today (Half-Life included!), Digital Extremes takes a step in the right direction with Pariah's storyline. One, your enemies aren't aliens. Two, you're not some kind of "tough guy". You are actually a perfectly normal doctor named Jack Mason who is transporting a patient infected with a mysterious virus on a spaceship in the year 2520, where Earth is now a nearly uninhabitable place, and space travel has become common. While the spaceship flies over planet Earth, it is shot down by an incoming missile, and you nearly die when the ship crashes onto Earth. After healing your wounds and picking up some weaponry, enemy soldiers (who are humans, by the way) come out of nowhere and you must do whatever it takes to survive. The plot unfolds as you progress through the game, eventually telling the player about everything that led up to the events in Pariah. I won't spoil it here :) Play the game and see it for yourself.
You don't heal your wounds by picking up generic "medikits" or "health boosters" or whatever. Instead, as a doctor, you are equipped with a healing tool that injects you with materials that replenish your health, just so long as you have the energy for it to work. As such, the game interface uses it as a weapon, and it can also be upgraded using weapon energy cores to speed up the injection time and increase the power of the healing tool. Injecting too much of the healing tool at once results in visual blurriness for a few seconds. When you sprint in Pariah, your vision blurs as the wind goes right past you, and after a few seconds of sprinting, you will become tired and cannot sprint anymore. In addition, you cannot wield your gun while sprinting. Such small touches help increase the realism and immersion of Pariah.
An amazing achievement in first-person shooting games, Pariah is one of the best first-person shooters ever made. It might not be Halo 2, but it's right up there, and a definite blast to play. So if you liked the Halo games, you'll still be completely absorbed by Pariah's single-player and multi-player components.
