I'd like you to know that I put a significant amount of thought into this question. Having an inner debate on what to judge a favorite on. You can't justly say Jason, or Michael Meyers because they had no lines or actual acting, not to mention the fact that there were almost always different actors used for each movie. I also looked at villians vs heroes. Did I base my favorite on creep factor alone, or were any actors in any horror movies viable candidates.
I guess it goes without saying that I probably overthought this process. But I finally came up with one.
I am going to say Will Smith.
The only reason I say this is because he ALONE carried I Am Legend. Very few actors could have pulled off an entire movie almost entirely by themselves, but he did, and it was a great movie.