It has been 12 years since Cameron unleashed the phenomenon that was Titanic and real fans would have to look as far back as 1991's Terminator 2 for their last proper dose of his incredibly epic action (True Lies, while fun, really doesn't count). So the anticipation for Avatar has long since reached fever pitch and beyond.

Thankfully for the patient masses, Avatar has turned out to be the biggest and best event movie of the year, perhaps the decade. The story is pure Cameron simplicity – a paraplegic ex-marine is given a chance to walk again through the use of a unique alien body, called an Avatar. It is his job to gain the trust of the natives so that a greedy corporation can steal the precious metal from their lush moon. Jake's (Sam Worthington) crippled main character is the perfect point of contact for the audience – not only is he new to the visual delights of Pandora but his disability means that every moment in his Avatar body is one of glorious freedom from the confinement of his chair. When the Corporations intentions become more sinister, Jake must choose between his new found place with the natives and his own race and fight for what he believes in.

Avatar combines parts of Pocahontas and Braveheart with a liberal dose of Space Marines into an epic whole that takes nearly three full hours to unfold. We could criticise that length, the weak story and the hammy dialogue. We could attack its thinly-veiled ecological message or the frankly bizarre spirituality in its second half but honestly nothing can spoil the experience while you are enveloped in it. And a large part of that is down to the brilliant use of 3D – which is both subtle and incredibly effective. Til now, we have been making movies with 3D elements, Avatar is the first truly 3D film and might well prove to be one of the most significant things to happen to blockbuster film-making since Star Wars.

Cameron is also pushing the envelope with truly photo-real CG – something which has been promised for years but has finally been delivered with Avatar. The interactions of the characters with the environment is incredible and the detail on the faces of the motion-captured leads (Worthington and Star Trek's Zoe Saldana) bring them to life. You will believe totally in their performances, representing another quantum leap in tools which have rarely been used for anything other than spectacle.

Make no mistake, Avatar is an important film from a technical standpoint but it is also great entertainment. The world of Pandora is a stunning spectacle from scene to scene and as Jake learns more about the Na'vi the film approaches the kind of light hearted adventure story which has been absent from movie theatres for years. Then the final act explodes into tragedy and desperate action, with the final half hour a blistering life or death struggle that has to be seen to be disbelieved.

Over the coming days you will be hearing a lot about Avatar, and some of the critical reaction is bound to focus on its weaknesses in a bid to appear appropriately reserved and objective. But this is not a film to be dissected or examined, rather one to be experienced with a warm crowd, a great sound system, in 3D as you bask in the knowledge that the movie-making master is back!