what anime got the best OST?  

I have only a few anime soundtracks but I'd say I really like the soundtrack of Rurouni Kenshin/Samurai X and Yuyu Hakusho/Ghost Fighter. I like most of the opening and ending themes. I also like the soundtrack of the Dragonball series because I like most opening and ending themes plus the movie songs included in the soundtracks. So far, I can listen to at least more than half of the soundtrack CD's songs than other animes.

I think the best OST has to be the from the anime, Neon Genesis Evangelion. The song title is "Fly Me to the Moon", which I am sure many of us have heard it before from several singers. This version in the anime has a jazzy feel, very soothing to the ears.

hello :) for me there's a lot of anime that have good soundtracks i'll list here almost all of my favorite,D.Gray Man almost all of it's soundtrack is good,Ouran High School Host Club,Shakugan No Shana,Romeo&Juliet there's still more but i forgot the titles already :D

Helsing! :D
That song "Shine" of the band Mr. Big.

Well best ost would definitely be Death Note's... I mean it's so nice to listen to, whether the time of day, and coming to think about it, I'll just put it on while I am writing this. That's better. Also I would recommend Claymore's... It has some good ones there. For the rest, I am not quite sure :)

There's actually quite a few that I like. I'd say that Rurouni Kenshin and Initial D has some great OST. I don't pay much attention to the inserted songs but the ones for RK are really memorable and recognizable. I like both the Japanese and Eurobeats for Initial D. The Full Metal Panic series and Hikaru no Go anime also have great OSTs.