O_O We actaully have a thread for this.
Well Mega Man X series goes without saying, but the first one really takes the cake. Especially the last stages where as you ascend to the top of the last fortress, the songs fit the stages perfectly.
1.) Heroic charge in and attack; it's very energetic sounding.
2.)
In stage 2, the song gets more depressing and darker as X has to go through it alone.
The last 2 stages aren't as great but they follow the same pattern of gradually getting darker until the last stage music which is this quieter yet more ominous tone. And the scenery matches this gradual change to boot! Very well played-- crazy how you can make such a nice atmosphere with just 16 bits.
Then when you get to the ending song, it's very subdued and bleak, which ends the story. Now, that gave the X series its distinct feel aside the original series. Well, at least until they decided to milk the series and extend it long after it should have ended, and having supposedly dead characters hide themselves so they can repair themselves.
Other good X series songs
The later is like adrenaline pumping.
Then there is Chrono Trigger; how can i forget that theme song music...
It also has what is probably one of the best battle theme of all time. It really brings in that you better have leveled up and collected your tech points... or you're gonna get the worst ass kicking of all time.
And then it gets bested... by the same game. :O
Both give you the sense of "Holy fucking shit". I don't think anything else from Square I've seen can best it though they sure come close.