As a fan of (some) anime, I have encountered soundtracks I both like and dislike.
Honestly, like anime itself, the majority of music in anime is pretty ******** terrible. Most anime have shitty looping electronic tracks, generic synthesized sweeping-violin pieces, and some hipster "look, I'm just like Cowboy Bebop" jazz tracks. Even worse are the series which rely on "J-pop" for their base influence musically.
This isn't to say all anime have bad soundtracks. Though, generally, good soundtracks come with good anime. Boogiepop Phantom has an awesome scuzzy, noise-based OST. Famously, Cowboy Bebop has some pretty amazing jazz. Witch Hunter Robin had some truly great orchestral pieces, each song of which had an intense and distinct flavor. So on an so forth.