radio station in Tokyo

what is a really good radio station in Tokyo?

By "good", I assume you mean one that plays good music, which is subjective for each of us. So your question is too vague.

However, here are some radio stations that you might want to check out.

Shibuya FM - limited reception area, must be close to the Shibuya area, but plays my favorite music without much commercials.

InterFM - definitely not my fav, but most DJs are bilingual and speak in English

Tokyo FM - not bad, usually better than J-Wave.

J-Wave - okay and sometimes very good.

Yokohama FM - If you have a cable connection, you might be able to catch this station. Like Tokyo FM and J-Wave.

By "good", I assume you mean one that is popular in here.

Japanese stations, especially on the AM side, are not specialized in certain area, but all of them are "all round" stations. They run music, talk, news and commentary and sports depending on the time of a day.

According to the rating servey, TBS at 954Khz is the most popular, and NHK at 594 and Nippon Hoso at 1242 follow.

If you are a Japanese language learner, I recommend you to tune to short monologue programs. Examples are
+"Itterasshai" with Anju Suzuki, App. 7:35-7:38am, Mon.-Fri., at Nippon Hoso at 1242KHz.
+"Hachi-ji no good story" with Masahiko Ueyanagi, app. 8:14-8:20am, Mon.-Fri., at Nippon Hoso at 1242KHz. Summary (in Japanese) is available at their web site. http://www.1242.com/goodday/?id=3