Here is another obvious pairing from the BIG TWO in super-powered comics. Demon versus Gargoyle.
I am more of a fan of DC's The Demon, but I did like the 1980's Defenders; which was my first recollection of Marvel's Gargoyle (and I think the best written that I know of). Please recommend anything you think is a good representation of Isaac in comics. I've been out of the loop these days when it comes to the sequential word.
So, I'd have to say that The Demon Etrigan would be the victor, but that's just me. Fight amongst yourselves.