I can't believe no one mentioned Zelda 2 for NES.
Unlike many boss battles like with Zelda or Mario games where it is nothing but a trick that you rinse and repeat a few times, fighting your shadow in Zelda 2 was nothing but pure skill. Not to mention, getting to him in the first place was an amazing feat in itself.
This was the only game in my life where I felt it was like a real life fight. No slow paced turn based fights, no tricks, just pure out attack/jump/blocking skill action that is relentless and fast paced.
On another note:
final fight cd wrote: so it takes a full hour to fight a boss?
how is that fun or enjoyable at all? that sounds awful. mental note: never buy or play FFXII.
No it doesn't take an hour to kill the boss... perhaps gamerforlife rushed the game and tried to beat him low leveled. I killed him in 25 minutes or so, and a lot of the fight is cut scene.
FFXII is a good game. I didn't get into it as much as FFVII and FFVIII but if you are into RPG's you should check it out.