I think that television has definitely helped the exposure and profitability of professional, and even amateur, sports. There has been a youth sports explosion in recent years, that many attribute to exposure on television. One only has to look at the impact Tiger Woods has had on the interest and participation of minorities in golf to realize the effect television has on sports.
With that being said, I personally don't care for much of the showboating and drama that the increased exposure has led to. So there is one negative.
Television did for modern professional sports what radio did for baseball in the 1920s, it gave the average American access, anywhere in the country. Except now, viewers can see virtually any game between any team, as opposed to just the Yankees and Dodgers from the old days.
Ad revenue from television has led to a larger number of teams being sustainable, which has broadened the appeal of pro sports and given a shot in the arm to local economies in major urban centers across the country.
I think televised sports has increased the interest and awareness of sports for young people. My son and his sports-minded friends would rather watch Sportscenter than Spongebob. His interest in sports has made him want to try new sports and push himself to excel at sports. He has forged new friendships because of the different teams he has been a part of. Being able to watch various sports on television gives him a chance to see the "whole picture" of a sport -- how various defences are run; the role of various positions on a team. He is a genuine fan of his home teams and that is part of the bond with his dad. While there are all kinds of legitimately negative points to make about televised sports, I think that the connection that people make through sports is a positive thing.
There are a number of different approaches to this. Certainly, on the one side, it has definitely helped sports by getting a larger audience and attracting more money. However, on the negative side, professional sports has arguably been led into directions that it may not have wanted to go in as it now has to consider the media of television and finances to remain viable. This has led for example to a more restricted viewing of certain matches as companies such as Sky buy up the rights to show particular matches, reducing audience numbers.