I think part of the apparent staticness of SGA had as much to do with the fandom as the show itself -- the fans definitely latched onto a particular era in the show's history as far as character relationships, cast, and overall style of the show (season two/early season three), and continued to carry that through in fic and meta, whereas the show moved on and did other things.

Yeah, I've been thinking that. It's like that fandom was living in a bubble somewhere between season two and three.

But still, the way the Stargate shows evolved over time doesn't compare to AtS. Angel did really quite radical changes both in tone and overall structure, every season has a totally distinctive feel.