Well... the difference betweene GB in adventure mode and GB in event51 is actually very big.
I could knock out the 51-GB at 194% with a smach attack from Mart. The Adventure-GB on the other hand... I had to get him to something like 400% before I could smach him away!!!
And the adventure GB also hit harder + dodgeroll sometimes. I've almost never seen 51-GB dodgeroll...
Man, imagine him at "very hard..."

ANYWAY... I've beaten him with Roy too...
Almost same strat as with Marth but I countered more with Roy since his counter is more effective against strong attacks like Warlock Punch and stuff.
Time: 3:42. 1life left. (I had 2 lifes left with Marth by the way...).