Is this a common problem with the SF2 hu? I just thought that the more stuff thats in the card the more stuff can go wrong, or do hucards just poop out for no reason?
It's pretty rare for a HuCard cart to "poop out for no reason."
I *do* have a Ghouls 'n Ghosts (SuperGrafx) cart that has corrupted sprite graphics for one single enemy (the vultures in the first area) but is perfectly fine for the rest of the game.
I also have a Spin Pair cart that is completely non-functional (exactly like your SF2).
Someone else, I think Black Tiger, had a problem similar to my GnG issue with a Bonk's Adventure cart a long time ago.
Whoever brought up the fact that the SF2 may be a little thinner than other games is right. When I first got my copy of SF2 it wouldn't start up and I thought I had a bunk copy. I cut a piece of cardboard from a matchbox (very thin cardboard) that was the same size and shape as a HuCard and I have to insert it with the game when I want to play it. It pushes up the cart just enough so it makes contact. I know you already tried the "tape" trick but you might want to try a piece of thin cardboard before you write it off completely.
Beyond that, it's usually only a matter of cleaning the contacts.