Back in the early days, SNL actually did some decent political humor, stuff about the CIA and wars in Africa. But that was of that time, and once the show became a cultural landmark, all that disappeared. They can still be funny now and then, but like I said, it's pretty surface. It certainly helps that Fey's a dead ringer for Palin.
The only late night comedy show that really did cutting satire was "Fridays" on ABC, from 1980-82. They skewered Reagan, the Christian Right (at a time when everyone else was afraid of their supposed clout), and set sketches in Salvadoran refugee camps, depicting torture and death squad activity. It was great stuff. And of course, they were cancelled after ABC put "Nightline" in their slot. A much funnier show.
Dennis