Ahh! The final battle against Amakusa (second theme). (First) Mega Man X 4 - Final battle against Sigma. Apocalypse themes from both X-Men VS Street Fighter and Marvel Super Heroes VS Street Fighter. (Last)
I really can't wait to play the full game. I can't identify other music, but I can hear the music from Double Dragon 3: "Battling final boss Noiram/Cleopatra", "Blood relation" from Castlevania: Symphony Of The Night or Dracula X: Nocturne in the Moonlight, Double Dragon 2: 1st battle of the Mysterious Warrior, and Megaman x4 battling 1st and 2nd form of Sigma. I also hope we can see the Mysterious Warrior make a come back. That be awesome. By the way, Pactrico, when you have a chance, you and your brother check out Double Dragon: Legacy. It's awesome.
Epic final battle music! And I really loved the bits of Kaioh's theme (Fist Of The North Star 2) and Amakusa's 2nd theme (original Samurai Shodown) that were fused into this.