Yeah, Lewandowski will probably pick up a couple of goals during the group stage but Poland won't last long enough. They'll go through but face either Holland or Germany in the quarter-final and that's that.
Klaas-Jan Huntelaar looks like the best value for money to me. He's been in an insane goalscoring form this season. If he starts he'll end up as Hollands top scorer. They don't really play to Robin's strengths but Huntelaar will score all the odd goals irrespective of how Holland get the ball into the box. That's just what he does.
It wouldn't surprise me if we had a couple of players ending on 5 goals each just like in the World cup so it might be best to check the rules in detail before putting in the bets. My guess is that one of the other (potential) top scorers will come from Germany. They have a favorable potential fixture list coming up, provided they win their group, and they're bound to last a while. Podolski, Müller and Klose all look promising. If it ends up being decided by assists again, like in the World cup, it will definitely be a German player nicking the golden boot.
Spain don't have any out and out goalscorer with Villa injured. I expect them to last to the final but the burden will probably be shared between Llorente, Torres and Soldado.
Eduardo might be an interesting outside bet too. I can see Croatia finish second in their group at Italy's expense and they're highly capable of beating anyone from Group D in the QF.