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Uncharted 2: Among Thieves
What already worked Uncharted: Drake's Fortune gave players a first-rate action movie experience, a winning combo of gunplay and puzzle-solving, plus incredible visuals, snappy dialogue and impressive voice acting.
What got better Among Thieves raised the emotional stakes, went whole hog on the fantastical aspects of the search for Shangri-La, and not only added multiplayer action but managed to tweak it with a few twists — like its Plunder Mode — that made the online competition feel uniquely suited to this franchise.
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Half-Life 2, Half-Life 2: Episode 1 and Half-Life 2: Episode 2
What already worked The moody story of the initial Half-Life gave more attention to character development and story-telling than other FPS games.
What got better In short, everything. Instead of a single location, the HL2 games take players all over an oppressed, paranoid world. These three sequel installments are set years after the first game and have theoretical physicist Gordon Freeman returning to join the human resistance on an Earth that's been taken over by the extraterrestrial Combine. Since the games' debuts, the gravity gun's become an iconic weapon for gamers everywhere and scrappy freedom fighter Alyx Vance has launched millions of nerd crushes.
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God of War II
What already worked The game's gratifyingly gory hand-to-hand combat matched its rageaholic anti-hero Kratos, who disemboweled and dismembered every mythological creature that stood in his way.
What got better Scale. On-screen enemies got bigger and more numerous, with about double the number of boss battles. More characters from Greek myth show up, even if it's just to get dispatched in even more painful ways.
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Resident Evil 4
What already worked The long-lived series brought a creepy, claustrophobic brand of Japanese survival horror to the United States. Players were set upon by slow-moving zombies in an abandoned mansion where ammo and health-restoring herbs were always scarce.
What got better RE4 refocused the franchise, with a simpler plot and a tight, over-the-shoulder camera angle that made the action more immediate and threatening. Plus the setting of a foggy, cult-controlled Spanish village brought back the fear of the unknown. The shift from hoarding herbs and bullets to frantic combat reinvigorated the series for a whole new generation of fans.
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Assassin's Creed II
What already worked The action/adventure game combined parkour-influenced running, jumping, and climbing with the ability to sneakily kill just about anyone anywhere in medieval Jerusalem. Ubisoft's best-seller rewrote the book on what to expect from an open-world game.
What got better For the second trip down Desmond Miles' DNA helix, developers gave new ancestor Ezio more options for mayhem in Venice and other cities of the Italian Renaissance. You can hire courtesans to distract guards or use mercenaries to do the dirty work for you. The swordplay showed increased flexibility and depth, too, with more weapons and tactics than before. Underneath it all, the game's virtual Italy sported a more varied, vibrant population than any other free-roaming game so far.
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Legend of Zelda: The Ocarina of Time
What already worked The Zelda franchise pretty much invented the action-adventure RPG genre. Mixing the derring-do of swordfights with the statistics-based rules of Dungeons and Dragons provided a template for more than a dozen future successors.
What got better Maturity. The first 3D Zelda delivered clever gameplay based on time travel and learning to play haunting tunes on a magical Ocarina. Where Ocarina of Time really shined, though, was its surprisingly thoughtful take on the recurring fable, with Link's adventures becoming a coming-of-age story. OoT was where Zelda grew up, taking a generation of gamers with it.
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GTA: San Andreas
What already worked Rockstar Games had arguably already changed video games forever with Grand Theft Auto 3 by creating an urban sandbox where players could script their own unique chaos on a huge scale. The follow-up GTA, Vice City, sharpened the satirical edge and cinematic ambitions of the series, with celebrity voices and a grimy rise to power straight out of Scorcese's playbook.
What got better Size and tone. It expanded the scale of GTA, with a customizable lead character and by three distinct cities with tons of new vehicles and side missions. San Andreas also gave the series its darkest emotional tones, as conflicted thug Carl ''CJ'' Johnson comes home to bury his mother and desperately try to keep his biological and street families alive.
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Mortal Kombat II
What already worked The once-controversial martial arts fighting series pioneered a gaming style lifted from the 1970s grindhouse kung-fu double features. The signature element of Mortal Kombat games comes in the form of their Fatalities — finishing moves that graphically burn, behead or otherwise kill the loser.
What got better Production values. New characters, new settings and a more polished experience overall gave rise not only to Fatalities with even more arterial spray, but also LOL-worthy Friendship and Babality finishers, too.
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Burnout 3: Takedown
What already worked British-based developer Criterion had success with the first Burnout game, which rewarded players for ''offensive driving'' stunts. Burnout 2 added an addictive Crash Mode that sent racers hurtling into packed intersections to rack up as much damage as they could. Racing games had never seen this kind of carnage before.
What got better The Burnout threequel introduced the Takedown move, where players could slam and ram opponents into other cars or barriers — and then get treated to a glorious slo-mo cutscene of the car twisting and exploding into so much shiny wreckage. The takedown added another layer of strategy to already tense racing action and vaulted Burnout to the top of the arcade-style racing category.
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What already worked Halo: Combat Evolved managed to replicate the smooth, quick shooting action that PC gamers had been enjoying for years. Master Chief became the mascot for the Xbox and its eventual successor.
What got better Halo 2 changed multiplayer gameplay on consoles forever. Through Xbox Live, developer Bungie and Microsoft created an ecosystem of devoted players who tested themselves against each other night after night.
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Mass Effect 2
What already worked Bioware's 2007 action-RPG masterpiece Mass Effect succeeded in presenting a believable fiction with characters and relationships who felt real.
What got better ME2 boasts leaner, meaner controls for gunplay, skill points, and squad management. The political intrigue's bumped up a notch, too — add the stunning visual overhaul and you get a game that might just surpass its predecessor. That's the whole point, right?