Almost anything Yuzo Koshiro. His best is probably ActRaiser, but ActRaiser 2, Shinobi 2 and Streets of Rage 2 are good too. Don't know what he was smoking when he made SoR3, cause that soundtrack was garbage outside Crazy Train.
I'm also a fan of Live-A-Live, Demon's Crest and 7th Saga 2: Mystic Ark though I heard the guy who composed 7th Saga 2 died very young.
I'm huge into video game OSTs, but my favorite still goes back to the PS1 days. Chrono Cross tops all others in my opinion. Yasunori Mitsuda is easily my favorite video game composer, and this is one of the games that solidified his spot there. Every instrument is interesting (whereas the bass is sometimes very basic with other composers) and the melodies and harmonies are always memorable.
There are songs from other games that I would consider to be my favorite, but as an overall soundtrack, Chrono Cross is just too well-constructed to consider anything else.