I know this may just be something generic and simple but I really like the electric guitar tone in Mario Kart 8. Does anyone know how to achieve this sound?
What kind of guitar should be used, what kind of amp and what pedals? 

high gain amp
humbucker/other highouput pickup.
some sort of tube screamer.

there are way too many variables to know what the person recording used.
Probably humbuckers, high gain, moderate reverb, little/no delay.  Something often overlooked is the volume interacting with your guitar, it sounds like it's just a little below the point of getting feedback.  Only really makes a difference on the sustained notes though, and probably isn't worth antagonizing your neighbors as you try to figure out how blaring it needs to be to get the perfect hint of feedback :P