Does anyone know if these two characters are actually the same or not. By that i mean do they exist in the same universe?
Saturday Night Slam Masters game page: http://www.giantbomb.com/saturday-night-slam-masters/61-16684/

Isn't that really two different questions?  As far as I can tell, there is no evidence that El Fuerte and El Stingray are the same character.  The only thing that we seem to know about them for sure is that both are masked Mexican wrestlers.  However, In Mexican professional wrestling, masked wrestlers (luchadores) are extremely common, so this alone proves nothing.

However, they most certainly do exist in the same universe.  The Street Fighter franchise has crossed over with the Final Fight franchise (several Final Fight characters appeared in the SF Alpha series) and the Final Fight franchise crossed over with the Saturday Night Slammasters franchise (Haggar appeared in all the Slammasters games.)  So an El Fuerte/El Stingray grudge match isn't out of the question if Capcom so chooses.

Another point is that if Capcom had wanted El Fuerte to be El Stingray, they probably would have just made him into El Stingray, as they have not been at all shy about crossing over these franchises before.  There would be no need for the mystery, unless this is their hidden homage to the world of luchador wrestling.  But since they created a new character with a new name and a new design, I would have to surmise that he is truly intended to be a unique character.