I like the radios. The problem is that some people doesn't like to open their minds for new types of music. Worldwide FM and FlyLo for example are the best radios i've listened for a while. But the majority of metal/rock fans are close minded to hear other musics than metal. Look for new things. Open your mind.
I am a die-hard metal fan and my favourite stations are Flylo, Mirror Park, both talk radios and West Coast Classics. You are the one who should stop assuming and open your mind.
I think the radio stations seem to be smaller because they have certain songs that play every time you do a certain activity i.e. you enter a cab (Tatuado), jack a car from a lady in vinewood hills (Rihanna/West end girls), enter a strip club (Scandalous), play as Trevor (Channel X) etc. etc. etc.
Oh, and Channel X seems to have only a few songs because R* chose typical 2min. punk songs, so compared to a station with average 3min. songs it seems a lot smaller selection. I have listened to every station and there are at least two decent songs on every one EXCEPT the pop and mexican channels. They don't have necessarily bad music but I just don't like the genre.
You might be but metal fans are seriously some of the most closed minded people you can meet. Trust me my cousin is one and if it is not some guys making music with guitars he thinks it sucks.