Occasionally at the end of Arcade mode, I'll be able to fight Akuma/Gouken in the extra stage after the boss battle (with Seth).
Unfortunately, this doesn't quite so often. I've played through Arcade Mode, only for the character cutscene to trigger right after the Seth boss battle fight, and sometimes getting to Akuma. I've only fought Gouken once, and I have no idea how I was able to fight him.
How can I tell when I'll fight Akuma/Gouken at the end? Is there a requirement I need to do (take minimal damage, combos, etc.?) to actually fight them?
Best Answer
There are actually 4 secret bosses (in SSFIV AE and USFIV). Assuming you have selected Arade mode with 1 round per game you need to meet the following requirements to be able to fight them:
These requirements increase once you choose multiple rounds per game.
You can only fight the boss if he is a member of the cast for your game. This means you cannot fight Oni or Evil Ryu in Street Fighter IV or Super Street Fighter IV. Here is a list of all bosses in the different versions:
TIP: You can use the second controller as a last resort. If you miss your Super/Ultra on Seth you can press Start and you will enter a 2 player game. Once you win you can resume Arcade mode and fight against Seth again. This is not counted as a loss.
Source: http://www.xboxachievements.com/forum/showthread.php?t=314180