Halo 2 might actually live up to the name of its predecessor, but it stumbles a little in the face of its own hype.
Not that it really matters that much. Halo has been about bringing a focused FPS game to a home console that didn't compromise on a PC version. The main thing the original Halo did right was perfect the dual analog stick control scheme for use with first person shooters.
To that end, Halo 2 can basically be thought of as more of the same from the original game: Gun fights galore in responsive first person right in your living room. In truth, it is not an ignoble pursuit.
There are some minor distinctions: Master Chief's shields (life) recharge differently such that he now seems to take less damage but the shields recharge quicker. In play terms that usually means that if you get trapped in some crossfire you might find yourself toasted pretty quickly, but the typical lucky distance shots the AI will pepper you with that hit infrequently won't be as much of a hassle as they were in the original. There are new weapons now as well as adjusted or tweaked favorites, which try to balance out some of the previous games' issues (particularly with multiplayer). For the most part the efforts were successful although you still notice in multiplayer matches several weapons lying around ignored by most players.
The graphics in Halo 2 look a little better than before, although cutscenes use a clipped approach to texture loading which allows them to jump in after the scene has started to reduce load times. Most players probably would have preferred a short wait than to watch the jarring texture pop throughout the game.
Overall the single player campaign is fun: You run around and shoot a lot of bad guys, drive some nifty vehicles and even get to step outside of Master Chief's shoes and play as a Covenant warrior known as the Arbiter. The Arbiter controls almost exactly the same as MC so the differences are pretty subtle between the two characters, but it makes for some interesting story ideas and possibly sets the stage for more adjustments to what players should expect from this series.
When all is said and done Halo 2 is clearly a second act: The "end" is nonexistant, settling for a brutal cliffhanger rather than any kind of implied resolution. This may be frustrating for some players but shouldn't prevent anyone from actually playing the game. If Halo 2 is enjoyable enough, Halo 3 should be a no-brainer and numbers suggest that plenty of people will line up to see how Master Chief fares in his continuing adventures.
Where Halo 2 really stumbles is with the online Live options. The matchmaking capability of multiplayer versus matches can be a lot of fun, but randomized map selection seems to either be too random or not random enough as you may find yourself playing in the same arenas repeatedly. The addition of more maps some time after the game's release helped some but there still seems like there should be more maps and especially locations from the campaign mode would be nice.
The biggest sin committed by Halo 2 is the lack of online co-op play. If any game ever screamed for such a feature, this is the game. You can play co-op but only via LAN or split-screen. It is a given that online versus play is by far the most popular option right now, but one has to wonder: Is that because that's all game developers are giving us or is it really what gamers are demanding? It could be argued that the popularity of team-based versus games (Counter-Strike, team modes in Halo 2, Battlefield, etc) and the guild structures that pop up in so many online RPGs indicate that people want to play with their friends as often as they want to play against them. When you consider that most versus games don't allow players on opposing teams to communicate via voice chat (or text chat for that matter), the appeal of teaming up with a buddy seems obvious. Why Bungie and other game developers tend to treat co-op like some disposable afterthought in most games is yet to be known, but someone needs to set them straight and the sooner the better.
Aside from the one glaring oversight and the texture issue, Halo 2 shows a lot of polish. The musical score is a very effective blend of haunting classical/orchestral arrangements and driving rock music that works marvelously and always fits the tone of the level or area being played. Enemy AI is effective especially at the higher difficulty levels and animations are smooth. Most loading times are minimal to nonexistant as you move nearly seamlessly from one area to the next and draw distances are nice and long. The game looks great during play and the sound effects are inspired, right down to the hollow, distant echo of gunfire and explosions while out in space trying to defend your defense network from attacking Covenant swarming the hull of your ship. Vehicle control is specific to the vehicle in question and may seem sloppy at first but mostly just takes getting used to and of course the FPS controls are as close to flawless as possible.
Overall it may have been impossible for Halo 2 to meet everyone's crazy-high expectations, but it does a pretty good job overall. If only they had managed to get the online co-op into the game this might have been a near-perfect game. As it stands, it's impressive if not stunning but as with the first the game is more exciting for its potential than for what it really is. Viva Halo 3.