wipeout64 is in fact very playable with pj64, you might not see the title grafices at first but if you wait awile and press a bunch a bottons you'll soon see a mode select simbol ( a little W at the bottom of the screen) keep pressing "A" and a stage will load up.
as a matter of fact it runs reel smooth without any missing grafices (that i noticed) while your racing in the stages. but i only tried 1 stage.