Although the greatest bodybuilder of all-time was Anja Langer (this is not a debatable point, so don't even offer your alternative suggestions), Sharon Bruneau was one of the top 3 hottest, and a strong argument could be made for placing her #1.
She's credited with one of the most schmoe-friendly lines ever, too. During an interview back in the early 90s, when asked what men (esp her husband) thought about her physique, a giddy Sharon replied, "My hubby just loves my muscles!"
To this day, she remains the #1 fantasy to many schmoes worldwide.