@xerox
If you really wanted to write a good review, it must be a full review. First off, you must have played the game to a certain extent to know all the aspects of the game and to understand everything about it, which in most cases is fully completing the game so that what you are saying is credible and makes sense. You also must understand that your review is not just to say the good things and the bad things, but to critique the game, to add suggestions and to point out the flaws so that when the developer reads your review, he will say "Oh my, how could I have missed that" or "That's a great idea, it seems implementable."
Now good reviews are always organized, so take your time to organize the introduction, body and conclusion. Think about it like an essay. Your introduction should include at least some sort of short analysis to that transitions into the body. The body should include things like Gameplay, sounds, effects, story, etc. You can call these things sub-bodies, where in gameplay may have it's own paragraph, and so might the others. Now it's up to you to how many major things you will judge, but just note that a full review is the best review, leaving out nothing in the game.
Now your last part is to conclude, basically to summarize everything you've said, and make those really major points stand out. The conclusion may or may not have overall rate the game, but make sure those major points are out.
You can have a choice to say, the good things of a game, or you can leave it out and mainly focus on the bad areas. Either way, just remember, make sure your review doesn't bore the reader to death. An article is always more memorable if you say the things that should be said in a way that keeps everyone hooked.
This is usually how I write reviews. Though, if you really are serious about making outstanding reviews, check out Youtubers who review games in unique ways but still get their point across. My suggestion: AngryJoeShow. Don't listen to what he's reviewing, but try to listen to how he organizes, entertains, and reviews any game. You can learn a lot about reviewing from other reviews.