If you want a striker with a Pele/teenage Ronaldo-esque scoring ratio (30 goals in 30 games, rather than 'just' 15-20), you must sacrifice all skills that are not essential to putting the ball in the back of the net.
The reason for this is that the game really tries to limit the number of '20s' in any one player - try to give him more than 3-4 of these and you'll see all his attributes slide.
Set Tackling, Positioning, Marking, to 1.
Set Finishing, Off-The-Ball, Dribbling to 20.
Experiment with:
Pace, Acceleration (at least 17, I prefer 19-20, which of course requires more tough decisions on what other skills to sacrifice... such as: Long Shots, Set Pieces, Heading, Jumping - one would prefer a super-striker to be 20 at these as well, but in my experience this is asking for too much, and you'll end up with maximum stats in the 17-18 range)