The ring grants the user powers based on how powerful the wearer is, frodo was not very powerful so it only granted him sight into the wraith realm and invisibility.
If Sauron were to use it though, then all of middle earth would be doomed.
Which is why they waged war to destroy the ring and Sauron forever, since the two are linked together.
Sauron put most of his power into the ring, without it he is considerably weaker, with it though he is extrodinarily powerful, destroy the ring and his power in middle earth is destroyed with it forever, kill Sauron without destroying the ring means that you only destroyed his "Avatar" and soon he will return because of the rings existance.