You guys! copperbadge wrote the GREATEST SGA FIC IN THE WORLD. It's a Torchwood/SGA crossover, where Torchwood manages to take over Atlantis. Which, really, says everything that needs to be said about SGA.
Quis Custodiet Ipsos Custodies. Ianto neglected to introduce himself as he informed the senior staff that Atlantis was now under the jurisdiction of Torchwood, whatever Torchwood is. Set during S1, pre-Siege.
Seriously, though, the whole thing wins the freaking universe.