It may not look it at first, but Syphon Filter 2 does a good job of amplifying the best bits of the original.
+ Cranked-Up: The set pieces are bigger, the arsenal expanded, the bad guys tougher - all this, combined with more, longer levels, means you get more of everything that made the original good.
+ More Stealth: Many more of the missions require extensive stealth than before, offering a nice counterpoint to the mayhem; and thanks to the new close-quarter weaponry, their design is much more challenging and interesting than those of the original.
+ Challenging: Its predecessor wasn't exactly a breeze to get through, but right from the start, you'll be made to sweat in order to get through the waves of (much deadlier) enemies.
+ 2-Player: It's not exactly brilliantly done, and would have been much more interesting if you could have even a couple more players, but multiplayer is a nice addition that offers some reason to return to the game once in a while.
- Awkward Movement & Camera: One thing that definitely hasn't changed one bit since the original is the clumsiness of moving and aiming - who would have thought a nigh-on unkillable secret agent would be so clumsy to control?
- Few Additions: While there are some nice ideas in terms of set-pieces and suchlike, there are almost no concrete additions to the game in terms of new moves, other than perhaps the close-quarters killing and some automatic jumping. Even the visuals look identical!
- Meaningless Character-Switching: While it's nice to switch between playing as Gabe and Lian, and to some degree Lian's missions tend to be more stealth-oriented than Gabe's, it's still a shame that there really isn't any tangible difference between controlling the two of them.
All in all, if you enjoyed the original Syphon Filter, chances are you'll like this too - it doesn't make any dramatic changes, but at the same time amps up everything that's good about the series. It might be a little dated by how clumsy it is to control, but it's still worth checking out!