Well as far as I know, Ray Reardon, Terry Griffiths and Alex Higgins never had a 147 in a pro event but it wasn't really as big a thing back then, they played more defensively and the cloth was slower. If we limit this to say the last 25 years or so where the game is played more aggresively and with better cloth, then I can think of 3 that stand out:
Paul Hunter 146
Matthew Stevens 145
Ken Doherty 145
On a side note, I would have thought for sure that Stevens not only would have had a 147 break by now but would have won the World Championship...he had so much promise. He's still somewhat young enough to turn it around I guess.