your too predictable..for example, at 1:50-56. He knows your going to use your get up attack, so he uses his second jump and most likely stomps you, setting more combos up. I think you have to mix your stuff up. the stock from 2:09-2:32 was a great example of you doing well.
also i think you play too aggressive sometimes, as it can be dangerous especially going against gannon. hes got a very great defensive jab, and long range tilts with pretty good knockback. I noticed that he would get you A LOT with the jab, meaning hes forced to play defense since you play aggressive.
ALSO, i believe your having trouble not because of your mario but because of GANNON. when gannon approaches with a FAIR, and you shield and block it, you cannot immediatley shield grab to counter since:
1)the opponent may DI away
2) the FAIR of gannon, if blocked, pushes gannon away.
gannons side b does the same thing. if you try to grab after, most likely you will be tilted.
AVOID BEING ABOVE GANNON, ESPECIALLY BY PLATFORMS! gannon will spam UAIRS, which have GOOD KNOCKBACK, DAMAGE, PRIORITY, and it comes out very quick.
I also noticed you like to approach with the UAIR yourself. This is a good approach, however I recommend it only at medium percent. against gannon, this approach is nearly useless, since gannon is one of the heaviest in the game and he could easily crouch cancel and counter with something. nairs will knock him back.
dont get me wrong, im not saying DONT USE UP AIRS. use them when hes in the air, not as an approach.
one last note; I like your complexity with the edge guarding. however, you could go real simple with that towel ;p
EDIT: I ALMOST FORGOT. I agree with the post above me, but not just against gannon. Dairs from mario are very under-rated. VERY. you may want to experiment.