Best PC Game
World of Warcraft Wrath of the Lich King: While I haven't yet experienced what is supposed to be a bevy of great endgame content, leveling in Northrend is some of the most memorable leveling I've done. The dungeons are all fantastic, and the quests/storylines are all really well done and very detailed. Death Knights are incredibly powerful, and fun to play (along with an absolutely astonishing quest line), and several key additions like siege weaponry make World of Warcraft feel newer than before.
Best Xbox 360 Game (Exclusive)
Gears of War 2: Gears of War 2 simply takes one of the best Xbox 360 games and makes it even better with some slight and significant changes in its story, multiplayer and overall look and feel. While it has some shortcomings, it is worth mentioning as the best Xbox game this year.
Best Playstation 3 Game (Exclusive)
Metal Gear Solid 4: This is almost too easy. Metal Gear Solid 4 is the culmination of an amazing story, phenomenal presentation and production values, and just all around great and varied gameplay. While the story stands out among all of these, the acting merits some recognition as each voice actor does an absolutely incredible job at adding to the drama and intensity of this amazing game.
Best Wii Game (Exclusive)
Super Smash Bros. Brawl: With simply the large amount of characters, and a great online mode, Super Smash has never been better. While nothing much is changed as far as gameplay is concerned, it is still a very intense, competitive game to play either by yourself or with a group of friends.
Best PSP Game
God of War: Chains of Olympus: With a game as incredible as God of War recreated in almost an identical fashion on the PSP, this game is a technological achievement. The graphics are flat out phenomenal, and it looks almost just like the PS2 versions, which are still very great looking games to this day. The gameplay is just as smooth and fluid as previous games, and there's plenty of awesome powers and weapons, along with awesome bosses to fight.
Best Nintendo DS Game
Chrono Trigger: While it's a remake of a older, yet great game, Chrono Trigger's story stands out as one of the most creative and unique for its time and this time as well. The combat is just as fresh and adds more strategies to fights. The characters, bosses, and plot turns are all very memorable and well done, and while certain additions aren't as great as you may hope, the game overall is still great and will hold your attention for many hours.
Best Multiplatform Game
Grand Theft Auto IV: It's not really fair to give an entire platform to one game that's on multiple platforms. Grand Theft Auto shines in that packs a ton of great stuff into one package. A large bustling city, a dark, yet compelling storyline, characters that are interesting and humorous, unlimited amounts of freedom to do what you want. All of these things make Grand Theft Auto IV one of the best games of its kind, and sets the standard for future games.