All data from espnfc.com
I've prepared a report involving the study of the top goalscorers at specific clubs during the 2013/14 season. I have taken all their goals to account, and prepared them like this.

Goals against Tier 1 teams gets 5 points.
Goals against Tier 2 teams gets 3 points.
Goals against Tier 3 teams gets 2 points.

Tier 1 teams include Real Madrid, Barcelona, Atletico, Chelsea, Liverpool, Manchester City, Bayern, Dortmund, PSG, Juventus, Roma, and Napoli.

Tier 2 teams include EPL positions 4-8, La Liga positions 4-8, Bundesliga positions 3-5, and any teams faced in European competitions.

Tier 3 teams are the remaining teams not associated with Tiers 1 and 2.

Players involved are...

Alvaro Negredo
Sergio Aguero
Yaya Toure
Olivier Giroud
Wayne Rooney
Daniel Sturridge
Luis Suarez
Eden Hazard
Arjen Robben
Mario Mandzukic
Thomas Muller
Robert Lewandowski
Marco Reus
Antoine Griezmann
Gareth Bale
Cristiano Ronaldo
Karim Benzema
Diego Costa
Lionel Messi
Neymar da Silva
and Alexis Sanchez.

Here are my results.

1. Cristiano Ronaldo (156 points)

Tier 1 - 11 goals (4x Atletico, 3x Juventus, 2x Bayern, 1x Barcelona, 1x Dortmund)
Tier 2 - 21 goals (4x Sevilla, 4x Schalke, 3x Kobenhavn, 3x Galatasaray, 3x Sociedad, 2x Valencia, 1x Villareal, 1x Bilbao)
Tier 3 - 19 goals

2. Lionel Messi (115 points)

Tier 1 - 5 goals (3x Real Madrid, 2x City)
Tier 2 - 18 goals (4x Valencia, 3x Sociedad, 3x Milan, 3x Sevilla, 3x Ajax, 1x Bilbao, 1x Getafe)
Tier 3 - 18 goals

3. Diego Costa (93 points)

Tier 1 - 2 goals (1x Real Madrid, 1x Chelsea)
Tier 2 - 15 goals (3x Vienna, 3x Milan, 3x Bilbao, 2x Sevilla, 2x Valencia, 1x Porto, 1x Sociedad)
Tier 3 - 19 goals

4. Sergio Aguero (74 points)

Tier 1 - 1 goal (1x Chelsea)
Tier 2 - 16 goals (4x CSKA, 3x Tottenham, 2x United, 2x Everton, 2x Pizen, 1x Southampton, 1x Arsenal, 1x Newcastle)
Tier 3 - 11 goals

5. Thomas Muller (70 points)

Tier 1 - 4 goals (2x City, 2x Dortmund)
Tier 2 - 6 goals (3x Wolfsburg, 1x Arsenal, 1x United, 1x CSKA)
Tier 3 - 16 goals

6. Karim Benzema (69 points)

Tier 1 - 4 goals (2x Barcelona, 1x Atletico, 1x Bayern)
Tier 2 - 9 goals (2x Villareal, 2x Sevilla, 2x Schalke, 2x Galatasaray, 1x Sociedad)
Tier 3 - 11 goals

6. Luis Suarez (69 points)

Tier 1 - 0 goals
Tier 2 - 7 goals (3x Tottenham, 2x Everton, 1x United, 1x Southampton)
Tier 3 - 24 goals

7. Marco Reus (67 points)

Tier 1 - 5 goals (2x Real Madrid, 3x Bayern)
Tier 2 - 6 goals (2x Wolfsburg, 1x Leverkusen, 1x Marseille, 1x Napoli, 1x Zenit)
Tier 3 - 12 goals

8. Gareth Bale (64 points)

Tier 1 - 4 goals (1x Juventus, 1x Barcelona, 1x Dortmund, 1x Atletico)
Tier 2 - 8 goals (2x Schalke, 2x Villareal, 2x Sevilla, 1x Sociedad, 1x Galatasaray)
Tier 3 - 10 goals

8. Robert Lewandowski (64 points)

Tier 1 - 0 goals
Tier 2 - 8 goals (3x Marseille, 2x Zenit, 2x Wolfsburg, 1x Arsenal)
Tier 3 - 20 goals

9. Arjen Robben (63 points)

Tier 1 - 5 goals (4x Dortmund, 1x City)
Tier 2 - 6 goals (3x Schalke, 2x CSKA, 1x United)
Tier 3 - 10 goals

10. Mario Mandzukic (60 points)

Tier 1 - 0 goals
Tier 2 - 8 goals (2x Wolfsburg, 2x Schalke, 1x Leverkusen, 1x United, 1x CSKA, 1x Pizen)
Tier 3 - 18 goals

Others...

Alvaro Negredo - 59 points
Olivier Giroud - 56 points
Yaya Toure - 54 points
Daniel Sturridge - 53 points
Antoine Griezmann - 53 points
Alexis Sanchez - 51 points
Eden Hazard - 46 points
Neymar - 45 points
Wayne Rooney - 45 points

Points per goal

1. Ronaldo - 3.06 (51 goals)
2. Neymar - 3.00 (15 goals)
3. Robben - 3.00 (21 goals)
4. Muller - 2.92 (24 goals)
5. Reus - 2.91 (23 goals)
6. Bale - 2.91 (22 goals)
7. Benzema - 2.88 (24 goals)
8. Messi - 2.81 (41 goals)
9. Hazard - 2.71 (17 goals)
10. Griezmann - 2.65 (20 goals)
11. Aguero - 2.64 (28 goals)
12. Costa - 2.58 (36 goals)
13. Negredo - 2.57 (23 goals)
14. Giroud - 2.55 (22 goals)
15. Sanchez - 2.43 (21 goals)
16. Rooney - 2.37 (19 goals)
17. Mandzukic - 2.31 (26 goals)
18. Lewandowski - 2.29 (28 goals)
19. Toure - 2.25 (24 goals)
20. Suarez - 2.23 (31 goals)
21. Sturridge - 2.21 (23 goals)

HOPE YOU ENJOYED

+1 from me... It must of taken you a really long time for you to do this. You should also consider the impact of the goal whether it was a game winner or just for delivering a dagger.

But overall, it is really nice. I enjoyed it.

@Chanakya

Thank you.... I wanted to introduce the 'score changing' factor as well, but it is too difficult to throw in both. Maybe I'll do a separate one later.

If you're basing them on difficulty, then don't you think penalties should be worth lesser points then normal goals? I understand it is difficult, just a suggestion (although applying this logic you would also have to value freekicks more, etc).

I may agree with Murderer, i was avoiding puting a negative comment due to the efforts and the active contribution of dynast, a very good member here.
But i barely see how a PK can have 5pts even against juventus, some late goals at 4-0 or 3-0 when the oppositon had already given up, rather than an equaliser goal or a late winner goal even against a small team still defending for their result as little devils...
edit : The only reason i didnt comment mate, i put the +1 for the informations and went.

@Murrderer

Yes, but ESPNfc does not show me if/when goals are from free-kicks or penalties. I would have to do that from memory. I can remember all of Ronaldo's, Bale's, Benzema's, and Suarez's goals, but less of Messi's, Neymar's, and Alexis', and almost none of the other players because I don't watch every Bayern or City game. It is too difficult to include that attribute in. But I can do something similar with the score-changing factor.

The factor being: goals while team is winning count as 2 points, goals while team was drawn count as 3 points, goals while team was losing count as 5 points. Etc, etc.

I realize it is difficult and sort of needless, which is why I +1'd before posting and added that it's only a suggestion. Good OP nonetheless.

wow Luis Suarez less than Thomas Muller

^ And Benzema tied with Suarez too. Also notice how Costa is miles ahead of Suarez.

Very nice and detailed information. Thanks for sharing.