There's really something special about sequels. Usually, there are few artistic reasons to make them as they are pure cash cows. Just look at the top 50 grossing US movies and count the franchises. With TERMINATOR, the first film left open many possibilities for a sequel (or two, or three). Creator James Cameron was basically re-making the initial film with his T2 sequel adding a twist on the menacing T-800 cyborg character played by star Arnold Schwarzenegger. A new villain sprang up in the person of Robert Patrick, a smaller wiry liquid metal robot who gave the T-800 more than he could handle.
That trend continued with T3 maintaining T2's heroic status for the T-800 and adding Kristanna Loken as a female evil counterpoint more advanced than any before, yet this film was made without Cameron's involvement (lest we forget, Cameron did make an interstitial sequel for Universal Studios theme parks between T2 and T3).
Alas, in T4, the writers from T3 concoct more Terminator business, and do their best to further the legend. Characters and dialogue from the first film reappear in different states, and much is made over the post-Judgment Day scenario in Los Angeles. Happily, we are treated to several surprises and new directions in the Terminator mythology. Director McG's pallid palette and drab proceedings depict a post-apocalyptic world with little to visually recommend, but he delivers the action and sense of fascination of the earlier films.
One key error might be the lack of a true villain in this new film. With Schwarzenegger, Patrick, and Loken providing formidable respective foils in the first three films, we are left with few faces to the computer defense system, Skynet, in this new film. This, despite a cleverly placed Helena Bonham Carter as a resurrected cybernetic force who lived in the pre-Judgment day world and transformed into a higher being in the futuristic world.
Some new characters appear, the best of whom is Sam Worthington as a renegade misplaced character named Marcus whose true identity is even unbenownst to him. Though clearly not a pure hero, Marcus comes closest to putting a new spin on the human-cyborg relations of the earlier films. Another fresh face and undeniable force onscreen is Moon Bloodgood as Blair, whose natural beauty and innate power captivate all of her scenes. Of Korean, Irish and Dutch ancestry, Bloodgood's career should get a serious push from her role in this film.
The only question remaining in the T films from this point is, what's left to do? Curious is that John Connor, who's wife is pregnant and reaches a climactic seemingly expiring point in the story, lives to fight another day, dispensing with the intriguing idea of his offspring becoming a new leader. Perhaps that is being saved for T6 in lieu of T5.