Yea, some games were optimised.. mostly a lot of the more popular games from Nintendo and Rare. They could be indentified from regular 50HZ games by the lack of horizontal boarders at the top and bottom of the screen. Iam not too sure if they are just as fast as something in 60HZ though.
Of course with introduction of newer systems came the option to switch games into 60HZ, considering most TVs in PAL territorys support 60HZ anyways, kinda makes sence