I own both SR3 and Dead Island.
SR3 literally took me through the entire game from beginning to end. It was one of the most entertaining games I have played, and at times I still hop on with some friends on steam to just mess around and cause havok. Very broad game, lots of things to do, plenty of challenge also. Overall, I love it.
Dead Island is also pretty fun, but as it is said, it gets pretty dull after a while. Playing with people helps to kill some of the effect, but once you get into the town, it just drops off. I definitely would say pick up SR3.
Your steam id?