As noted, Comedy Central recently aired a marathon of what they claimed were the "50 best" episodes of Saturday Night Live as selected by visitors to their website. They never posted the actual list anywhere but someone sent me a rundown of which episodes were run.
And as expected, there were none from the first five seasons since Comedy Central didn't have the rights to those. There were none from the last three for the same reason. There was one from 1980, one from '82, one from '86, one from '87 and one from '88. The vast majority were from the years 1996-2000, with eleven episodes from 1997 alone.
Now, this may be because the viewing (and voting) audience on the Internet is younger than we think and inclined to favor the years when they first discovered SNL. It may be that Darrell Hammond voted a few thousand times. Or it may be that the voting was kind of a sham and the folks at Comedy Central just put on whatever they felt like showing. My natural suspicion of polls conducted on the Internet leads me away from the belief that there's a substantial number of people who really assessed all the choices and came to the conclusion that SNL has never been better than it was a few years ago.
Then again, look at who we elect in this country.