Hm. Honestly? If you consider Sephiroth the amazing, suped-up on Lifestream warhero of SOLDIER, not Sephiroth thestupid, ugly, kill-him-in-four-hits final boss, I think it would be a tie, or a very close match, in Crono's favor.
Now, if we were talking Crono vs. Goose on the other hand, our redheaded hero is definitely screwed.