The first season of Stargate: SG-1 was very good. It had good stories, but it also had great potential to become something better. Season 2 has begun to realize said potential. Many of the episodes this season expanded on ideas and arcs from the first season, as well as introducing new ideas, characters, and locations. For example, we meet Thor (in his true form), as well as some of the other Asguard, a powerful alliance with the Tok'Ra is formed, the NID storyline is taken in new directions, and we learn about the builders of the Stargate system as well as the origins of the intergalactic U.N. from the first season episode, "The Torment of Tantalus". We also meet some new Goa'uld system lords, as well as see the destruction of an old enemy.
The actors (Richard Dean Anderson, Michael Shanks, Amanda Tapping, Christopher Judge, Don S. Davis, and Teryl Rohtery) all grew in their roles as Col. Jack O'Neill, Dr. Daniel Jackson, Capt. Sam Carter, Teal'c, Gen. George Hammond, and Dr. Janet Frasier. Not only did they prove their worth as their own characters, some of them got the chance to play others as well in the episode, "Holdiay". I'm sure that Judge liked that one because he got to play O'Neill, who is Teal'c's polar opposite.
The storylines were improved this year (not that they were bad last year), with some great examples being: "The Serpent's Lair", "In the Line of Duty", "Prisoners", "Thor's Chariot", "Secrets", "The Tok'Ra, Pts. 1 and 2", "Spirits", "Touchstone", "A Matter of Time", "The Fifth Race", "Serpent's Song", "Holiday", "1969", and "Out of Mind". There were a few groaners, such as "One False Step", but overall, this was an awesome season.