Bruce is an excellent actor.......but horror,.......I don't agree with that. Humor is his strong point......he is great at comedy. He can play horror and action aswell.....but comedy is his bread and butter. Out of the three Evil Dead movies.....he gave his best acting performance in AOD....which is an action/comedy flick.
Best horror actor.............Tony Todd...........just for his performance in Night of the Living Dead (1990).......throw in his performances in Candyman (he's excellent in all three....even though the last two movies suck) and Final Destination and it's a no brainer. He was the only saving grace in Final Destination 2.
Second best.......Robert Englund, not just as Freddy Krueger either. Although he did do a great acting job in NOES 1,2 and New Nightmare (the only three pure horror films of the series).....he also shines in just about any horror film he's ever played in........Wishmaster, Phantom of the Opera, The Mangler,etc. ........hell, he even shines in that turd of a movie "Urban Legend".
Donald Pleasance. His role as Dr. Samuel Loomis in the Halloween franchise makes him one of the best. He played the role so masterfully. His priest role in Prince of Darkness was also played masterfully. Although Pleasance was in many horror movie DUDs he was not the reason for these DUDs. He played his roles mastrefully and was a great actor. RIP Donald Pleasance.
Christopher Lee. He is tall and intimidating. that is why the Dracula role was given to him. He is the king of scary villains in horror films.
You can't narrow it down to one best actor... actually you probably can... Vincent Price. He personifies the horror gengre. Has been in many films such as The Raven and The Fly among others.