YES. I WAS WAITING FOR THIS POST.
So, the first one is obviously Kajiura Yuki. (Madoka, Fate/Zero, SAO, etc..) All her songs have the same "theme" who I think is absolutely beautiful.
Hiroyuki Sawano is good too (Shingeki no Kyojin, Kill la Kill, ...)
Takanashi Yasuharu for his lively OST...