Ted Turner wanted to buy syndicator King World because he figured its rich cash flow could help him bag CBS. Well, maybe it's a good thing his board scotched that plan. Investment bankers say King World, which boasts the top three syndicated TV shows, may be peaking. Reason: drooping ratings hurting all syndicators, due to competition from cable. Viewership for the top five shows this season is markedly down from that of the 1980s leaders.