If SG-1 had stopped after the 8th season I think it would have gone down as a legend, not fizzed out disappointingly like it did (up until the second movie, they kind of found their strengths again).
SG-1 is based around the movie of Stargate, and takes place two years after the events of the film. Two actors from the original movie came to renew their roles- Erik Avari and Alexis Cruz, who had relatively minor roles in the series. I’ll summarize the plot of the original movie so you can have some background. Don’t worry if you haven’t seen it, they explain everything in the show.
Stargate introduced a secret military base whose purpose was to examine an artifact found in Ancient Egypt that seemed to be evidence of a super-advanced ancient civilization. An Egyptologist, Dr. Daniel Jackson, who had been laughed out of his field due to his claims the pyramids were built by aliens, is brought in to try and translate some hieroglyphics on the cover stones of the Stargate device. Eventually he is sent to study the Stargate itself. Due to his work they are able to dial a combination into the gate, much like dialing a phone, and connect with an unknown location on the other side of the galaxy. Daniel is sent through the Stargate with a team of soldiers under the serious Jack O’Neil. He was given the secret mission of detonating a nuclear warhead if he found any threat on the other side. It was considered a suicide mission he gladly took on after the sudden death of his son (who shot himself with O’Neil’s service weapon accidentally).
On this planet they are welcomed by the chief of a tribe and his son Scarra, as well as his beautiful daughter who falls in love with Jackson. The whole planet is put at risk when the God of these people, Ra, arrives in a large ship that uses a pyramid as a landing platform. You learn that Ra was a boy many thousands of years before who was possessed by an evil alien creature (which gave him long life). The team eventually defeats him using the nuclear warhead they brought through.
O’Neil returns to Earth and Jackson stays behind on the planet to marry the chiefs daughter. O’Neil tells the military that Jackson died and that there was no life on the other world, keeping the military from going back.
SG-1 picks up two years later when the Stargate is activated and a small force comes through, kills most officers, kidnaps another, and leaves. O’Neil is brought out of retirement to lead a team to visit Skarra and the chief once again. He reunites with Daniel. This man who came through the gate and kidnapped the female officer also raids the village and steals Daniels wife.
Even though the command is angry at O’Neil for lying about Daniel and the others they allow him to lead a team after this stranger. Long story short: they realize that Ra was not the only of his kind, and Apophis, another alien, is planning on attacking Earth (the other aliens thought the planet had been lost when an uprising buried the gate in the first place). Apophis is a Goa’uld, a snake-like alien who burrows into a human host via the back of their necks and wraps itself around their brain stem, controlling their bodies. He implants Daniels wife with his mate and Skarra with another.
The team manages to get Apophis’ lead guard on their side, who is a member of a species called a Jaffa (slaves to the Goa’uld who have no immune system but a pouch in their stomach in which they carry larval Goa’uld until they are fully grown. The Goa’uld acts as their immune system). Teal’c, the Jaffa, helps them to escape and is taken in on the military base (he cannot leave but can go on missions).
The series follows O’Neil, Daniel, Teal’c, and Sam Carter, a brilliant female scientist who is credited with getting the gate to work again in the first place. The four explore the galaxy though different stargates (initially the military believed that it only went between the two planets, but they learn it goes to hundreds of thousands in the galaxy). The first 8 seasons deal primarily with their battle first to find Daniel’s wife, then to kill the Goa’uld and avenge her death (oops, spoiler alert!). They are aided in their war by the Tokra- a rebellious group of Goa’uld who refuse to take a host unless that host asks for them to do so and shares the body with them equally. Eventually they come across the Asgard, former allies to the race who built the stargate before being killed off.
Early on in the series there were some rough patches in the acting, but those were very few and far between, and I think the casting overall was brilliant. I’ll go through each lead actor in turn, but as a team they really worked well. The three leads who auditioned at the same time recount how they gravitated towards one another at the audition and became friends even before being told they were cast. The chemistry between them is brilliant and I absolutely loved it. I’ve heard people complain about the acting for Michael Shanks (Jackson), but I’m kind of on the fence here. Sometimes he’s brilliant, but every now and then he misses his mark. I think he hit his stride in series 4 and was pretty good after that. My absolute favorite episode is the one at the end of series 5 where he ascends, his acting is award-worthy (a fan actually thought he died and sent flowers to the set).