I think JDramas/Gameshows might be a little more helpful than most Anime. However, yes you should have basis in the language first. I took Japanese senior year and had to try and continue on my own this year because my College doesn't have it. I still talk to my Sensei, however, and she corrects my mistakes. It's soooo important to have a native speaker helping you through the process, especially if you have trouble learning languages. I don't see being able to have a basic conversation about magical flying samurai and 'What did you have for dinner last night?' as having
learned the language. It's a start. I just think people are mistaken when they think being able to recite lines from an anime makes them proficient in Japanese.
Agan, media helps
a lot with learning a language, especially live media. I listen to Japanese radio jockey's sometimes. Obviously because my Japanese is still very basic I can't understand 97% of what he's saying. But I'm really picky about pronunciation in any language so I feel it helps. Also, there's nothing wrong with just hearing it just to get used to it. My German teacher based many of our classes on watching podcasts, weather reports, tv shows, etc. in German. Again, we were all in advanced level, but it helped a lot to hear how the language is spoken in everyday life.
I guess my point here is that you can't actually
learn Japanese ONLY from anime, but it could help you out along the way if you've already been getting formal lessons.