I think my biggest contributing factor in sending me down the path to loving soundtracks was Rockman X. It had such an amazing soundtrack for a game of that day. And then there were Streets of Rage and Turtles in Time,great Beat Em Ups with great soundtracks. Actually, I still love these as much today as I did then, even in their original versions.
I also attribute soundtracks to my huge range in musical taste today as well.
Among my favorite series for listening are Blazblue and Guilty Gear by the amazing creator and composer for the games; Daisuke Ishiwatari
Dynasty Warriors has many great tracks to be heard.
I couldn’t name every series off the top of my head, but Falcom’s jdk Band puts out some great stuff.
As far as orchestral goes, Soul Calibur has some great music and from a few Tales Of games plus the God Eater series the amazing Go Shiina
Can’t forget SoundTeMP for RO, LaTale, and various other games they’ve worked on including TOS for much fantastic music as far as.
Ah, and various titles in the Sonic franchise. SA and SA2 had great soundtracks.
I am kind of rambling on here, so I may consider a more detailed listing if anyone is interested in going that deep into discussion as I could probably go on for hours XD