I've also heard that most anime can be raunchy, or mature (as vibrokatana put it) at times...
First, you have to separate anime from hentai. Hentai is pornographic and only makes up a small percentage of all Japanese animation. Unfortunately, these series have received a disproportionate amount of coverage by American media. This coverage has led many people to equate "anime" with "pornography," and spread further confusion regarding anime.
Yes, some hentai series get translated and brought over to the US. Yes, there are a number of "merchandising series," geared toward selling action figures, trading cards, and video games.
But there's also a great number of series that are never recognized by American mainstream media. One recent exception to that rule is Samurai Champloo. While there is some mature content, the series itself would be rated PG-13 if aired in American theatres. The characters are complex, the plot is well-crafted, and the character dynamics are excellent.
But it's still not as popular as Pokemon, because American audiences are programmed to associate animation with children. Why, I have no idea, because the Flinstones and the Simpsons were both geared toward older audiences.
