I know both MadTV and SNL haven't been as good as they were early on, but there are 2 diamonds in the rough...and both of them come from MadTV.
Aries Spears and Frank Caliendo
Aries Spears' Shaq impression, though not the most accurate, is downright hilarious with those crosseyes. Frank Caliendo is probably the most talented cast member I have seen in recent years. His John Madden, Bush, and Jay Leno impression are down to the wire...practically perfect. A true, true talent.