Best: They Live (1988)
Worst: Alien Siege (2005)
Some sci-fi hokum is built on premises so daft, the film is pretty much guaranteed to fail. In Alien Siege , the invaders turn up as they require human blood to cure a disease that's afflicting their home planet.
They need 8 million of our finest specimens, and one of the sacrificial offerings selected in the lottery is Heather Chase (Erin Ross), whose scientist father Stephen (Brad Johnson) vows to save her with an unnecessarily convoluted plan.
Thankfully resistance leader General Skyler (Carl Weathers) is on hand help, and incite cries of 'Look, it's Apollo Creed!' from viewers on the verge of nodding off.
Best: The Thing (1982)
The first of John Carpenter's superb alien invasion flicks of the 80s, this is an altogether more serious affair than They Live .
The Thing (part remake of The Thing from Another World , part re-adaptation of novel Who Goes There? ) keeps the invasion small-scale, with a shape-shifting alien parasite penetrating an Antarctic research station.
For all the deservedly-applauded grisly FX, the film is probably more memorable for the expertly sustained tension. It's taut from start to finish, with a particular spike during a blood test...
Worst: Signs (2002)
Up to the halfway in this invasion, you've probably been thinking you were onto a winner. It's directed by that M. Night Shyamalan chap, who did wonders with ghosts and superheroes in his two previous movies, you tell yourself.
Up to the halfway point, Shyamalan even convinces you he's pulled it off, gradually building a growing sense of unease as he zeroes in on one family in the build up to the extraterrestrial crisis. He even throws in a decent cornfield set-piece for good measure. He's done it again, you surmise.
It all plummets spectacularly once the aliens arrive though, undoing all the first half's good work.
The first glimpse of an alien (on a home video of a child's birthday party) deflates the tension with campiness ahead of the main arrival, which squanders the premise with one of the most insultingly silly denouements in recent sci-fi history, rendering repeat viewings void.
Best: Transformers (2007)
Any movie that takes a toy-line for its source material is going to be on the silly side, but who better to bring young boys' fantasies to life than Michael Bay?
You have to treat anything in the 'story' category as nonsense (come on, warring robots disguise themselves as vehicles for chrissakes), and enjoy the large-scale spectacle (erm, warring robots disguising themselves as vehicles for chrissakes!)
There's also just a smidgen of Spielbergian DNA here (he exec-produced) amidst the moments of Bay's bombast, evidenced in the lighter moments and the general sense of wonder at the giant mechanical heroes.
Worst: Transformers: Revenge of the Fallen (2009)
Part I may have been flawed but fun, but this sequel is an utterly joyless experience from start to finish. Revenge of the Fallen is peppered with so many glaring plot holes that it's just not worth trying to keep up.
Yes, you still get some robotic smash-em-up action, but you have to sit through gubbins mythology, offensively right-wing sentiment and the relationship 'traumas' that beset Sam and Michaela as he starts college.
Every new idea thrown at the screen - comedy sidekicks, robots that can disguise themselves perfectly as humans, everything that happens at college - is frustratingly bad, and insult even to those looking for a bit of simple Saturday night fun.
Best: Transformers: The Movie (1986)
Two decades before Michael Bay and Steven Spielberg got their hands on the property, the robots in disguise already had a decent movie, a spin-off from the animated series based on the toy-line.
Featuring Orson Welles in his final role as planet-sized Unicron, the movie had the guts to kill off plenty of characters (including Optimus Prime himself), and it boasts an awesomely cheesy 80s soundtrack.
Your age when you first saw this will likely govern whether you consider this a best or a worst though...
Worst: Transmorphers (2007)
This one comes courtesy of The Asylum, a straight-to-DVD production studio notable for churning out cash-ins at the same time as big blockbusters arrive, perhaps in the hope that people might mistake them for the genuine article (example releases include The Da Vinci Treasure , Paranormal Entity and Battle of Los Angeles ).
Transmorphers arrived at the same time as Bay's Transformers , although its story also rips off The Terminator as aliens (piloting giant robots) arrive on Earth in the present day, and force the humans underground.
The action picks up a few hundred years later when some plucky rebels decide to fight back against their mechanical oppressors, though the limited budget makes the post-apocalyptic wasteland look more like your local Laser Quest than armageddon.
Best: The Faculty (1998)
Robert Rodriguez and screenwriter Kevin Williamson (hot off Scream ) sent their otherworldly infiltrators into an American high school, with only a Breakfast Club -esque bunch of misfits standing in their way to global domination.
It's another Body Snatchers type set-up, with the invaders parasitically overtaking the teachers and the students. The resulting 'pod people' are left with an intense stare, a desire to spread the parasite, and an unquenchable thirst for water.
There's nothing hugely original on display here (there are nods to tons of invasion classics), but the genre mash-up is deftly handled and consistently entertaining.
Worst: Final Fantasy: The Spirits Within (2001)
Before this movie version of the classic videogame series was released, Hollywood scare-mongerers were predicting that it would mark the end of fleshy actors as we know them.
After its release, human thespians breathed a sigh of relief, realising that their jobs were safe for a good few years to come. While the animation of the 'photo-realistic' characters was jerky, unconvincing and almost zombie-like, the ethereal Phantoms, that suck the life out of humans in a post-apocalyptic Earth, do at least impress.
It's hard to tell if the animation would have seemed better or worse, had the story not been such impenetrable twaddle.
