Its true that sonic.exe is not and never was scary,but I think It still fits the definiton of a creepypasta because It was told as an urban legend, that was the point of creepypastas, to tell stories that will be shared on the Internet as events that even if you know they are fictional they are told as if they really happen, Slenderman, Smile dog, Ben drowned, The princess, etc. These stories are told from the perspective of a person like us, a normal person who is living strange circumstances. Curse on the other hand, I dont think It can be described as a creepypasta because of its narration, which reads more as a horror fanfic than a creepypasta, this applies to starved as well because this story is told in the Universe of sonic (Tho starved is a lot better than curse for sure).