GLaDOS sang it best back in 2007: "I'm making a note here: HUGE SUCCESS. It's hard to overstate my satisfaction". Huge success indeed.

Portal 2 is, in short, a terrific game, throwing you headfirst into a realm of intense and brain-teasing puzzles and great humor. The story is richer story this time around too.

Like its predecessor, Portal 2 is not an adventure game in the traditional sense, but genre fans will find plenty to appreciate in this story-driven obstacle course, because puzzle games don't get any better than this.

Pile on the "Oh, yes!" moments of solving some really great puzzles, and there's every reason to start thinking about Game of the Year accolades. It's that good.

With this sequel, Valve has ramped up the brain-cramping puzzle elements and expanded the cast with immensely lovable characters, and they did it just enough to make sure the whole thing feels fresh and interesting for the longer campaign.

A truly fantastic game, a worthy sequel in almost every way and a joy to play. It may not pack the surprise-factor of the original game – a fact which deprives GlaDOS especially of much of her early power – but it's still just as fun, fast, funny and fantastic as we'd expect a second Portal game to be.

Portal 2 includes groundbreaking gameplay, a collection of deep and nuanced characters, a completely insane story, and some incredible gaming moments you'll probably never forget.

The very short duration and lack of multiplayer were the most important shortcomings signaled by the community regarding its predecessor, so Portal 2 came to directly solve these problems, while at the same time further evolving the gameplay that was so beloved by millions of fans. If Portal was an experiment, a child who didn't know if he'll reach adulthood, Portal 2 can be seen as the teen years of the series. And if the evolution will continue in the same manner, I can't wait to see what it will look like when he'll be all grown up.

Portal 2 is fantastic. Its single-player provides ample amounts of genuinely funny and compelling narrative and some great puzzles, while the co-op takes the game's mechanics and pushes them to their absolute, playable limit. You're only getting around 10-12 hours after delving into both halves of the game, but it's a concentrated thrill, where its weakest moments are still standards that most developers can barely reach in the first place.

Portal 2 is a masterpiece and more than a worthy successor to one of the most innovative games in years.

In conclusion, Portal 2 is a textbook example of how to make a great game, but nothing more.

Without a doubt, one of the best games ever made. It's a game that not only seamlessly blends puzzle and adventure elements together, but makes a name for itself as a true "comedy" game, where witty dialog and laugh-out-loud concepts have been given an equal billing with the gameplay itself. It's funny, it's challenging, it's inventive, and it boasts memorable moments that will stick in your mind and make your hair stand on end every time you think about them.

Portal 2 delivers, and it does it in style, creating one of the most meticulously designed, thrilling and delightful playgrounds we've ever seen. It's a game with a magical take on momentum, where single bounds over tall buildings are business as usual, where every surface is a potential launchpad, and the entire experience is a belly laugh.

Portal is perfect. Portal 2 is not. It's something better than that. It's human: hot-blooded, silly, poignant, irreverent, base, ingenious and loving. It's never less than a pure video game, but it's often more, and it will no doubt stand as one of the best entertainments in any medium at the end of this year. It's a masterpiece.

Portal 2 is an excellent game. Maybe not as powerful as the first one, as it's a different one, but it's intelligent, witty and scathing. You should not miss one of the best scripts you'll see this year.

The writing is without peer and its execution brilliant, with the voice-over performances and details in visuals/animations rivaling anything Pixar has done on film. On top of all that, it's hilarious!

Portal 2 may be the best game of 2011. It may be the best game of all-time. It is certainly the best game you can play right now. I loved every moment I spent with Portal 2. I'm even enjoying looking at the game sitting on my shelf knowing how much fun I will have again someday when I revisit Aperture Science, alone or hopefully with a friend who may not have played the game. Portal 2 proves that you don't have to kill things to make a great game and more importantly…science is fun!

The game's quality stays consistently outstanding throughout; there isn't a minute of filler content to be found anywhere in single-player or co-op.

Impatience aside, Portal 2 is an exceptionally well-crafted, intelligent, entertaining, humorous game. You will laugh. You will feel like a freaking genius. You will want more. And yes, you will probably be hearing quotes from Portal 2 for the next three years.

So do we need Portal 2? Do I need it? Maybe not, but I'm sure as hell glad it exists. The portal aspect has probably reached its zenith in Portal 2, and given the way the game ends I don't think there's much room for a Portal 3.

Emancipation complete for Portal, which gets rid of his "bonus game" condition with a second episode that is certainly no revolution but still manages to justify its new status.

Portal 2 manages to exceed expectations without compromising any of the core gameplay that made the original so popular, and should easily be considered one of the best titles available so far this year.

Portal 2 expands on everything the first game did so well and makes it even better. Perfectly paced and adorably funny from start to finish, Portal 2 will keep on surprising you and challenge your wit right to the finish. In brief, everyone should play Portal 2, alone or with a friend.

By no means as revolutionary as the first game, but still lots and lots of fun. For some the overall playthrough time might be too short though, but Aperture is a place to visit again and again.

Ultimately, the biggest problem with Portal 2 is Portal 1, which was a lean mean meme machine driven by one of videogaming's most unforgettable characters. So when the sequel has a minor negative space problem, and closes with a credit sequence that I can't hum for the life of me, is Portal 2 ever so slightly disappointing, or was Portal 1 just flat-out ingenious? I suspect a little of both. But with this much awesome Stephen Merchant, and with my status as a frickin' genius puzzle solver reaffirmed, and with a unique co-op experience, it's like complaining that I was promised the moon and the stars, but I only got the moon.

The sense of novelty is diminished, but the thrill of exploration and puzzle-solving is still intoxicating, and it's amazing how Portal 2 manages to tell a better story with disembodied voices and spherical robots than most games can with full-on humans. Your return to Aperture Science is a joyful one in this immensely appealing, laugh-out-loud funny, and thoroughly satisfying sequel.

Sporting some of the best writing and voice work in years (as well as some deviously designed puzzles), Portal 2's single-player campaign is superior to its predecessor in every way. It's the co-op mode, however, that makes this 2011's first must-play game -- even for those gamers that don't like first-person or puzzle games.

Portal 2 couldn't be Portal, but it's the next best thing. It's a longer, funnier, more emotional plummet through Aperture's perplexing laboratory, and its meticulous detail, perfect pacing, and kinetic, mind-expanding puzzles make it a blazingly memorable experience. It's so damn memorable, already feel nostalgic about it.