I like the Re 2000 a lot but I think it's outclassed by the Ki-43. Maybe not hopelessly so.
The Ki-43 may was underarmed on paper, but it seems to have shot down an extraordinarily large number of enemy aircraft. The Re 2000 was not bad but I think the design wasn't fully developed yet at that point. I think Re 2001 (maybe with a Merlin?) or R2002 is a better match.