Why were the Jedi considered so powerful when they were easily defeated in the Geonosis areana and order 66?

why were so many jedi wiped out in attack of the clones during the geonosis arena rescue when they are considered to be the greatest warriors in the galaxy and can easily destroy 30 battle droids, why in revenge of the sith do all the jedi fall victim in the Jedi temple to an army of clone troopers and one fallen jedi surely many would escape before hand. the Jedi could be defeated but thousands of jedi in their own temple could surely destroy all of the invading clones. sure there were many survivors of order 66 but a handful of jedi over 50 of them were easily killed by darth and storm troopers.