This is tough, there are a ton of great announcers to choose from, but narrowing it down to the top 5..
1. Johnny Olson: His enthusiasm in all of his shows and great voice make him the all-time greatest announcer in my opinion.
2. Jay Stewart: His versatility shown on Let's Make a Deal with Monty Hall was awesome (re: zonk skits). Also, he had the greatest voice of any game show announcer (in my opinion).
3. Gene Wood: Announced on many shows, but of course best known for Family Feud. His interaction with Richard Dawson was great on the original Feud.
4. Rod Roddy: Considering the man he replaced on Price, Rod did one heck of a job and really created a niche for himself. He had the most unique voice of any announcer and could really work up an audience.
5. Kenny Williams: He was perfect on Hollywood Squares, and also funny to see on the rare Storybook Squares in his costume.