Most of the good ones are already given.
Slam Dunk is the only basketball anime I know. It's also one of the funniest animes out there. Can't help but laugh at Sakuragi Hanamichi.
Prince of Tennis is about bishonens playing tennis. It's absolutely hilariously ridiculously epically unrealistic. Just a sample to make you an idea :
(and there is worse, the last match in the OVAs looks more like a Naruto fight than a tennis game)
Taisho Yakyuu Musume is about girls trying to set up a baseball club about 100 years ago in Japan. It's excellent, but it's probably not what you are asking for. It lacks the "boys competing" aspect.