My rating for each episode in season four.
Episode 1: Small Victories -- Excellent
Episode 2: The Other Side -- Fair
Episode 3: Upgrades -- Excellent
Episode 4: Crossroads -- Fair
Episode 5: Divide and Conquer -- Good
Episode 6: Window of Opportunity -- Excellent
Episode 7: Watergate -- Excellent
Episode 8: The First Ones -- Very Good
Episode 9: Scorched Earth -- Excellent
Episode 10: Beneath the Surface -- Fair
Episode 11: Point of No Return -- Excellent
Episode 12: Tangent -- Excellent
Episode 13: The Curse -- Very Good
Episode 14: The Serpent's Venom -- Excellent
Episode 15: Chain Reaction -- Excellent
Episode 16: 2010 -- Good
Episode 17: Absolute Power -- Very Good
Episode 18: The Light -- Poor
Episode 19: Prodigy -- Fair
Episode 20: Entity -- Good
Episode 21: Double Jeopardy -- Excellent
Episode 22: Exodus -- Excellent
Season four is very emotionally diverse, with quite a lot of humor, as well as a bit of sorrow. The action remains strong, with some amazing special effects.
Although the Goa'uld threat is ongoing in the Stargate SG-1 universe, there are few actual appearances by Goa'uld in this season's episodes. However, their threat is not diminished, as the Goa'uld factor in, or directly influence, what happens in a significant number of stories this season.
The known situation with the Goa'ulds is little changed from the events of season 3, episode 13, "The Devil You Know." Apophis is in charge of Sokar's forces, and he is a potential threat to the System Lords, although he never quite crosses from potential to severe threat. Still, the realm of Stargate SG-1 does not feel stagnant; it still feels as though it is growing, and expanding, encompassing even more of the mysteries in the galaxy.
The theme that ties this season together is a more mature, and experienced, SGC and SG-1, learning about other life in the galaxy, while continuing with their mission to keep Earth safe from extraterrestrial threats. I think this is a result of the cast meshing together, and having a firm grasp of their characters, combined with some very good writing choices.
Season four is a tough act to follow, with some amazing episodes. However, season five holds on to the high quality level of performances, and stories, as well as providing some great adventures, and more.