I can most definitely tell the difference between Pepsi and Coke. They taste 100% different to me.~
As for 7-Up and Sprite, I can only mildly tell the difference... I've never had C Plus but I guess I can make up my own comparison : Crush and Fanta Orange.
I can taste the difference slightly with those as well, and I prefer the latter. <3
... I have a pretty extensive soda palette (sadly) cause I drink wayyy too much of it. >/////>