My memory is pretty fuzzy unfortunately. I recall that one would choose their fighter, which would have different abilities (magic or fighting etc). Then both would enter the screen from opposite sides to battle. The graphics were not the best. That's about all I remember. Not much to go on!
Yeah the closest I can see is what genpfault posted as a reply: Archon: The Light and the Dark. Hope that's it, otherwise I can't find much, either.