The original Syphon Filter was a great game. It mixed genres very well, producing a more action-oriented experience than Metal Gear Solid and providing it from the behind-the-back perspective that powered games like Tomb Raider. Syphon Filter 2 picks up immediately after the first game left off, both in story and in execution. While some features have been added, the resulting game feels more like a hastily-produced mission pack than a true sequel.
If you didn't play the original game to its completion, the plotline of Syphon Filter 2 won't really make any sense at all. The game assumes that you know the characters and the roles they played, and that you know that Gabe Logan, the hero from the first game, and his assistant, Lian Xing, have been sold out by the mysterious Agency, and it appears that the Agency is actually behind the Syphon Filter virus, which is currently running rampant throughout Lian Xing's body. Luckily, after each prerendered story sequence, a brief screen of text explains the action so you at least know what you're supposed to do in each level. The game uses a lot of video between levels, so much so that it takes up two discs, though this game isn't really much longer than the first one. Syphon Filter vets should be able to blaze through the first disc in three or four hours.
The mission design is a little bland. For the most part, it alternates between full-bore action missions and stealth-laced adventures, where you must restart the mission if you're spotted by an enemy. This levels give the game an annoying trial-and-error feel. You're forced to simply try a mission over and over again until you find the one correct path. In the early part of the game, you'll switch between playing as Gabe and Lian, but this is mostly to keep the story moving, as the two characters play identically.
This game adds a two-player deathmatch mode into the mix. You can select from many of the game's different characters and scaled-down versions of the one-player game's levels (some are locked at first), but the control, camera angles, and overall feel of Syphon Filter don't lend themselves very well to a mulitplayer component. Playing the game with head shots turned on makes it even more ridiculous, since anyone with any sort of head shot skill can clean up with little effort.
The control is largely the same as in the original game, but the analog portion has been refined. Gabe can now walk, making precision movement possible. Also, Gabe can jump over gaps. The jumping is handled automatically, so if you run at a jumpable gap, Gabe will leap over it with no input from the player. This can make some levels (the train level, for example, which features a lot of jumping) a real hassle.
Graphically, Syphon Filter 2 remains unchanged from the original. It still looks good, but at the same time the style of the animation and textures looks a little stale. Also, the sound and music are similar in theme, but the voice-over work isn't nearly as clean as the original's was. Some of Gabe's lines and vocal inflection really don't fit the current situation, making it sound as if he were lounging by the pool instead of taking heavy fire from entrenched enemies.
If you were a big fan of Syphon Filter, you may get a kick out of the sequel, but the lackluster mission design and super-convoluted story really cancel out the improvements to the game's control. If you missed the first game, it's a much better (and likely cheaper) game than Syphon Filter 2.