You'll still see sitcom reruns on CBS, NBC, and ABC stations in some mid-sized and small markets. For example, "Everyone Loves Raymond" reruns run at 6:30 PM weeknights on Spokane's NBC affiliate, and a search would show some other examples. But, of course, it is far less common than it once was.
Back in the seventies and eighties, sitcom reruns of shows like "All in the Family", "MASH", and "Golden Girls" ran on big-3 network affiliates in major markets, and got extremely good ratings for many years. 10:30 PM reruns of "All in the Family" were a fixture on our CBS affiliate in Dallas through the mid-eighties, and were subsequently replaced by "Golden Girls" for several more years. In many markets in the midwest and mountain time zone, either the ABC or CBS affiliate would run programs like "MASH" or "All in the Family" at 10:30, and would get far higher ratings than if they had aired the network late night programming in pattern (often, they'd beat "The Tonight Show" on NBC).
But as we moved into the nineties, the networks placed increasing pressure on affiliates to run late night programming in pattern, which killed the affiliates' ability to run these sitcom reruns in that lucrative time period right after the late news. With Fox and independent stations getting stronger, these stations were able to bid aggressively for off-network comedy reruns, and I suspect that the rising prices just made these programs un-economic for big-3 affiliates to purchase for daytime runs.
As for hour-long dramas in weekday syndication -- we're about to see a reappearance of this genre, with one of the "Law & Order" programs ("Criminal Intent", I think) due for weeknight broadcast syndication starting this fall. It will be interesting to see how it performs.
