I agree with RandomRob re: picture size, it sort of dominates your review
Now for my main point:
As pointed out above, it's very difficult to retroactively review a game, especially one as famous as HL2. I don't want to discourage people from attempting this, since it can serve as great writing practice, but as RandomRob correctly points out, you need to pay extra attention not only to what other writers have already said about it, but also to subsequent patches, add-ons and other aspects of the game and its release.
Your review is also a bit too glowing - if it is pointless to describe it in words, why are you trying?
Try going a little bit more in depth: for example, when you discuss gameplay - talk about the way vehicles are incorporated in the game, rather than just glossing over examples of ones the player comes across. Does the AI react well to your actions? Is the combat truly as realistic as you describe? In a relatively long complex game like HL2, you need to show why it outclasses other games from the same genre, and what influences it has passed on to future games/franchises.
One thing shone through in your review, and that was your enthusiasm for the game. Spend some time reviewing your piece to make sure it has a good mix of depth and accessibility, and you'll be in business