I have been a big fan of the show even when it seemed like all the talent had been sucked out of the show. The big deal really is the fact that it continues to be funny despite the change of cast every 5 years. This is a show that is has such a history as to be required to re-invent itself with only one major foundation over the last 25+ years. That foundation has been Lorne Michaels. I'm not really sure how funny he is although in the sketches he's in he seems to play the foil for most the zanies on the show is totally effortless. Being that straight requires some idea of how to be funny in my opinion. Regardless, the thing he does well is finds funny people when other shows are just not ready to handle their particular brand of nuts. I'll focus this comment to one particular actor though I think it does apply in general to most actors/actresses who get on the show and are new at some time.
Bill Hader. This guy is a goldmine. He has huge chops in the acting arena but you also get a voice actor to boot who I think is more intelligent and less irritating that Seth McFarland. For example, take the Vincent Price Holiday Specials he does on SNL. He is bringing to at least 2 generations the knowledge of the best and most sadistic of the 50's actors and actresses in unadulterated satire. The pure rampant drug use and alcoholism that is not only real but sadly funny because we all know our grandparents were weirdo's for a reason. Add to that the fact that he plays Vincent Price as the uptight straight man versus the screen part he seemed to be cast for over his career and you've got some intelligent comedy gold. It is also the reason that he gets to be part of so many ensemble comedy casts in movies that are actually funny and not related to Kevin James. (My dislike of Kevin James may become noticeable over time, so as a warning, I do not like Kevin James movies. Blame Hitch and my lack of ability to let things go.)
Finally, you get to see some great musical artists jump on the show and perform their number one hits followed by a late night version of something no one usually get to hear unless they are a fan and have the album. It is to this day still a great format and one that I am glad still exists. I expect to be going to bed at 10:30pm on Saturday nights soon and have my kids sneak downstairs to watch the show when they think I'm asleep. What I will really be doing is spying to see how much of the comedy they get and how much I'm going to have my wife explain to them the next day.