I also say
Mushishi has a exquisite OST. If you didn't like Toshiro Masuda in
Naruto, you might like him here. I especially love
Mushi Utage, but I think you're better off watching the anime than solely listening to the music. The music really does wonders bringing to life
Mushishi's world.
If you loved
Yakitate Japan! music,
Tengen Toppa Gurren Lagann's composer is the same person, Taku Iwasaki. There's a lot of wonderful pieces I can't name specifically one I like especially.
The best anime OSTs I've heard are
Ouran High School Host Club by Hirano Yoshihisa and
Hikaru no Go by Megumi Wakakusa. Amazing strings and nice piano flourishes. I'm a fanatic of them lately.
His and Her Circumstances by Shiro Sagisu deserves an honorable mention, but I didn't like the new musical direction as the anime got worse imo.