Although, now that I think about it, how about Chuck Barris? He had three massive hits, four if you count Treasure Hunt. While it wasn't as big as TDG, TNG, and TGS in my eyes, it lasted four years its first time out.
I was thinking about this earlier this morning. As much as we poo-poo on Barris, he had four shows which ran for at least 4 years. He had some stinkers (The Game Game, 3's a Crowd, Camouflage), but it seems his ratio of hits to duds is 2nd or 3rd best of any non-current production company, mainly referring to Endemol.
From a friend to the forum, here is Cleveland's broadcast history with some edits by me:
TJW 7:30-8:00pm Sept 77-Sept 78 on CBS affiliate TV-8
TJW 7-7:30pm Sept 78-Sept 81 on TV-8
TJW 7:30-8pm Spring 83-Sept 84 on TV-5
TJW on TV-55 from Dec 85 to at least Mar 87 at 11 PM to start, then at 6 PM with TTD until Sep 86, then to 10 AM when Crosswits premiered.
TTD on TV-5 from 7:30-8pm Jan 79-Sep 81
TTD on TV-3 from 1983-84 (airing first at 7pm and then moved to 1:30am)
TTD on TV-55 from Dec 85 to at least Mar 87, at 6:30 PM with TJW to start, but it was seen at 11 PM during this time period.