Stays true to its predecessor and adds a amazing physics engine. You can look past the technical problems.
Half-Life 2 is really great at keeping you immersed in the game better than any other FPSs out there and even better than its predecessor which redefined the genre. The lack of cutscenes allows you to find out through the gameplay what is going on by choosing to (or neglecting to) listen to certain conversations or watch certain scripted events happen. THis adds to the feeling that everything is actually happening and that you are an active participant in the story. It also is cool how the developers choose not to elaborate on the story too much which is realistic as Freeman likely wouldn't know what was going on around him.
The graphics are impressive and the world is well detailed although it is clear that many textures were simplified so the game could be run on the Xbox. The important stuff all looks fine but then yhou come across an overturned oil tanker with absolutely nothing but a plain grey texture mapped over it. The physics engine though makes up for the removed textures as it is the most impressive hting I have ever seen in an Xbox videogame (from a technical standpoint). Once you get used to the idea of everything acting realisticly you can use it to your advantage to do more lifelike things in combat when it comes to evading enemies or dipatching them. For example if there is a turret up ahead I can just carry a metal barrel along and use it as cover. The gravity gun really brings the physics engine to the forefront allowing any object to become a weapon (buzzsaws, barrels, propane tanks).
With all these improvements it is a shame that the AI isn't beter than it is. The combine soldiers will seek cover and all but for the most part they lock onto you and fire away until you or they die. They still end up doing cool things and using the environment but it still doesn't seem like enough of a leap over even the first Half-Life so many years ago. Strangely enough though this really doesn't hurt the game a whole lot. I don't know why, probably because of al the cool things you are doing while fighting the idiots I suppose.
The game is long enough but I really was not a huge fan of the driving sections which often streached on for far too long of a time. There were also performance issues such as frame rate drops and long (and sometimes too frequent) loading times. I also don't know why the checkpoint system can't act as hard saves which can lead to you forgetting to save before turning the system off thinking your progress is saved.
Still the complaints I have are insignificant because of how damn fun the game is. It is a must-buy for those with a PC, Xbox, or a 360.