Well... I've never counted Stargate as a SciFi masterpiece, but as a fun and enjoyable romp...
Season 1 was good, although there were a few episodes that in retrospect feels very campy and downright bad. The end of season arc (beginning with There But for the Grace of God) was awesome though...
Season 2 got better and worse at the same time. The storyline episodes were perfect (In the Line of Duty, Secrets, Fifth Race, 1969,etc), the fillers were mostly awful. (Think Bane or Spirits) too bad they ended the season with a clipshow.
Season 3 was a very stable, strong season, the main episodes were a definate improvement toward a serious storyline. One of the best seasons...
Season 4 had the funniest episode of any scifi show ever (Window of Opportunity), many good episodes (although not as great as s03) and only one or two bad episodes. (First Ones, Light, etc)
Season 5 was the best season in my opinion. Only two not-greats (Beast of "I still don't like this Unas shit" Burden and the Red Sky) and countless perfect episodes (Between two Fires, 2001, Wormhole Xtreme, Proving Ground, 48 Hours, Summit/Last Stand, Meridian (my 2nd favourite episode of SG1), Revelations).
Season 6 was something different. I loved Jonas, I missed Daniel. My other favourite season, three really bad episodes (Nightwalkers, Sight Unseen, Metamorphosis), the best episode of SG1 (Abyss) and of course the epic Full Circle... I loved almost all the episodes...
Season 7 was different again. This is where they started the "we didn't get cancelled this year again" routine... They WASTED Jonas, they had the most epic two parters yet (Fallen/Homecoming, Evolution, Heroes (OMG I LOVED IT), and of course Lost City) and the worst fillers yet (Enemy Mine, Space Race,Grace,Resurrection) and the start of Action!Daniel
Season 8 is where RDA's absence was really felt. They continued the trend of better and more epic storylines with worse fillers in between. (Avatar,Affinity,Gemini,what were they smoking?) But they finished the series with a bang (Reckoning, Threads, Moebius... perfect ending...)
Season 9 is a new series. But I loved it still. Mitchell is funny, smart, and Ben Browder is good. Vala is not. The Daniel-Mitchell scene in The Fourth Horseman is the scene that made this season for me. The Avalon 3 parter was good, Off the Grid and Scourge was horrible beyond words. I've seen better shows than this "Stargate Command".
Season 10 is like a proper Season 2 of a new series. It got better where it was needed (new Vala is better, the storyline is gripping, Pegasus Project, Quest, Line in the Sand,Shroud and Dominion is good. Uninvited, Bounty, Bad Guys and Family Ties are in the bottom ten of SG1 episodes ever. 200 could have been more fun, less in-jokes.
Then, when they finally stopped caring about being cancelled, they got cancelled.
But, I almost cried during the montage of Unending. Almost.
Ark of Truth was good, but WHO THE HELL PUT THE REPLICATORS there?
Continuum was better in style, but even worse in story. Solid acting from Browder and Shanks though....
Atlantis on the other hand is a different animal. They are better in character episodes, better in epic battles, but apart from some McKayism HORRIBLE at funny episodes (Irresponsible, Irresistable, Tower, Trio, Harmony, SERIOUSLY!!!)
But detailed review about Atlantis is for another post...