I know this may be inadvertent but egad! Did you leave out Zlatan??
Yep! I love Zlatan for what it's worth, but he would be in the 7/8 spots (or maybe the edge of Top 10 if I wake up on the wrong side of the bed). Consider someone like Eto'o, for example — wasn't always a match for mature Zlatan's domestic scoring record (though he did boast a 0.65 goals-per-game ratio at Barcelona and scored 400+ goals for club and country) or sumptuous technique or magisterial aura — but much more selfless within the collective framework, struck up a mutually beneficial with several world-class forwards over his career (including tricky ones like Ronaldinho, Messi, Henry), had a high workrate to lead the charge from the front, played a big part in Barcelona's Champions League campaigns (including 2006 and 2008 when they won the whole thing) and then tweaked his game to play ahead of Maicon under José, while staying out of Milito and Sneijder's way on occasions where he could have gone for glory, to lead Internazionale to the first treble in the history of Italian football. It's no coincidence that he excelled in 3 different teams under 3 different managers while having different remits to win
Big Ears.
Similarly, even though they created a lot of chances, playing as the #9 for Spain would have been overwhelming for most center forwards because you had to be decisive yet patient and calculating and un-involved for prolonged stretches — one might even contend that Villa played the role to its absolute peak. In a sense, he was the forward version of Schweinsteiger, a consummate provider of balance...and without his efficient and low-maintenance lethality the scheme could have been frequently blunted. As
@Gio said, he (or Klose) are quite possibly the best and most effective international striker(s) since Fenômeno.
It would be fair to argue that Ibrahimović would do be better as the main man at an underperforming club or a team that's on the rise (like Paris Saint-Germain) and take them to a good level as the attacking talisman who knits things together — but in an broader sense, the likes of Eto'o (while temperamental) or Villa would be a dream to coach because of their versatility, well-rounded skill set and team ethic (a bit like Benzema in recent years where he was willing to take a backseat to Cristiano and even Bale). Put them in the current Liverpool or City XI and they would do a really good job — can't say the same for Zlatan, and that's the crux of the issue. For all his profound gifts, Ibrahimović always needed a wide berth to perform at his best (hence why he couldn't coexist with some other
stars), wasn't always a very intense player wrt. pressing or leading the defensive organisation from the front, didn't give a good account of himself in the Champions League (which is the gold standard for equalizing/measuring the performance of players in post-modern period), etc.