Roughly, there's three big classes of good planar beings (lawful archons, neutral guardinals and chaotic eladrin) and three big classe of evil planar beings (lawful baatezu, neutral Yugoloth and chaotic Tanar'ri). So far, that's balanced, except wizards has published far more fiends than celestials.
Then there's various minor fiends and celestials of all kinds. I'd say that overall, good has a bit of an edge, as it has another major class, the angels. The only thing evil has to compare to that are the Gehreleth, and they are a bit anemic compared to the likes of Planetars and Solars.