This is the format that I think would be the best for reviews. It will only work with new games you get and not games you have played before. For games you have played before, just write an impressions or a review.
Impressions-
This is your first thoughts of the game. What you think about the game within the first couples hours (3-5 hours). This doesn't have to be long but just to summarize what your thoughts and to give people what the first thoughts could be.
Review-
This is after you have beaten the campaign or at least played the multiplayer for a long time. If it's multiplayer only make sure it's apparent in the title. The system will be out of 10 and will include the following categories. This can be more of a set of guidelines then how the game is rated.
Presentation-How the games is presented to the player. The way the maps are layed out, menus, overall feel of the game.
Graphics-How the game looks realistically as well as artistically. Also look at the graphics compared to other games on the system and not compared to others systems (example:Wii compared to 360)
Sound-How much quality there is in voice acting, sounds(explosions and little sounds), Music (sometimes a huge part of the gaming experience)
GameplayHow the game controls, plays (is there lag?dips in frame-rate?etc)
Lasting Appeal How long the game will keep your attention and how much replay value it has
Follow-up-
This is how well the game holds up after a long time of playing or when you come back to it, how good is it? Does it hold up to your first impression?
This set up is made so that the first hype experience you have doesn't ruin the review. Some games are better at first because you haven't gotten far enough into it or the hype wears off(ie, The Conduit)