Scott, Cameron, Fincher, Jeunet. These visionary helmers have made some of the finest movies of the past three decades. So, in theory, the Alien Quadrilogy should stand as a towering achievement, a franchise that never buckled under studio pressure or sold out to summer-event movie demands. The reality is somewhat different.

Few franchises have had such a strong start as Ridley Scott's never-topped exercise in sci-fi horror, a creepy blend of 2001 and Halloween - not to mention any number of haunted-house movies - which sees the original, Giger-gestated monstrosity offing Lt Ripley's (Sigourney Weaver) crew. And few film series have benefited from such a strong sequel as Aliens. James Cameron's stroke of genius was to reinvent Alien as a tension-grinding actioner while keeping many of the elements that made the first instalment so impressive (motion-tracking drama, shaky head-cams, flame-throwers, the kick-in-the teeth fourth act...). And all on a limited budget, too.

Then it all went wrong. Without a script in sight, and with a flock of squawking suits flapping around him, a young David Fincher made a brave attempt to end the story satisfactorily. By his own admission, he failed. Alien3 has moments of brilliance (the stark opening, the funeral/alien-dog-birth scene), but suffers from an unconvincing creature, a plot touched by absurdity and a baldy Brit cast whose incessant shouts of "wankahhh!" soon grate.

Fincher probably doesn't take much comfort from this, but he actually didn't end up making the worst movie in the saga (so far). That task fell to Delicatessen director Jeunet, whose initially intriguing Alien Resurrection gradually slides into risible farce. Without a doubt, the mewling `Newborn' remains one of cinema's silliest monsters , a depressing end for Giger's creation.

DVD Extras:

Almost overwhelmingly definitive. It's worth noting this is the first time we've seen the original theatrical cut of Aliens on DVD - a tighter, more effective movie than its relatively flaccid Special Edition twin. Plus, there's the Director's Cut of Alien, and Special Edition versions of Alien3 and Resurrection. The latter two possess worth only as curios. The Alien 3 SE sees the creature bursting out of a dead ox rather than a Rottweiler (go figure) and features an ill-conceived subplot in which Paul McGann's Golic sides with the beast; Resurrection SE opens with a dire comedy sequence involving a splatted fly and ends uninspiringly on a devastated Earth.Each instalment comes with at leastone multi-voice cast-and-crew commentary and a second disc. These all mix behind-the-scenes footage, stills, script drafts, FX breakdowns, archived talking heads and recent interviews.The Aliens Making Of material is the most rewarding, detailing how Cameron and the Brit crew got on so badly there was almost a walk-out. And the Alien extras are packed with great stories, including how HR Giger weirded out almost everyone he met. Alien 3's Making Of is more entertaining than the movie itself, especially when it reveals how the film could have turned out: Ripley landing on a wooden space station populated by Luddite monks. The Resurrection package is the weakest, but there are highlights, especially the featurette revealing how Sigourney Weaver's "impossible" basketball shot (where Ripley dunks the ball without looking) was done for real. There's also another disc - but don't get too excited: it's a dumping ground for trailers and such.Don't think we're complaining, though: if you're looking for a DVD set that'll take you weeks to plough through, this is most definitely it. Scribble it at the top of that Christmas list now...