The first season was pretty much a waste of time because of the writing and overdone low-key lighting. Aside from Robert Carlyle, who managed to do a lot with what he was given, everyone on the cast struggled with their fairly inconsistent roles. It didn't help that the writers' idea of arcs was to eschew having episodes that told a story that would progress a larger narrative in favor of stretching out stories over a few episodes for no real reason.
The first half of season 2 was just as bad as season 1, but they did more with secondary characters that were actually likable and managed to rehab Greer a bit. The actual story was still crap, but they managed to not make it as intolerable. Plus I think they upped the lighting a bit.
The last half of the season was fairly good, but they still had some problems with how poorly fleshed out the characters were and how one dimensional the bad guys were. The ending was kind of lame, because it reemphaiszed the whole "Eli is the character SG fans are supposed to associate with" thing that really irritated people back when the show began.