There are also several other feats to take into consideration. For one, Xemnas used lasers in his base form as well, which when Sora dodges in both 1 and 2, is a feat that kinda Supports the final Xemnas battle. Riku is also shown to be outperforming Sora at some points during that battle. Also, in DDD, Riku is able to battle against a Young Xehanort who's been powered up by Master Xehanort, and has Time Manipulation capabilities. This is also a direct way to scale Riku to Aqua Terra and Ventus, due to the Mysterious Figure. Riku also defeated the Armored Ventus Nightmare, another potential direct comparison. Also Rei, while Xemnas was probably altering Reality a little to his benefit, and his Kingdom Hearts was a fake, it's still a dangerous collective of Hearts, and has nothing to do with Sora and Riku's capabilities, as Xemnas wouldn't have boosted them in any way shape or form, so their feats are still valid. Maybe Xemnas's feats Can be slightly downplayed as a result, but that's like saying when Xehanort uses Kingdom Hearts, or when Ansem uses The Dark Guardian, that it invalidates their feats, which is Stupid.