I think when talking about Anelka huge talent, people often forget considering role.
What I meant is Henry is one hell of a world class player, however he is flawed. He preferred the freedom to roam, having access to central area, but he's the type that peeling away from opposition CBs rather occupying them.
Henry flaw is that he likes to drop deep to have many touches. He is dangerous even from outside the box, but in a disciplined, strong defensive team, CB's job is lessened once Henry as a sole forward was forced wide: less threat in the box. Arsenal had this issue all those year where they bemoan they didn't have a partner for Henry. Their fans, and even papers had to point out Arsenal might make wonderful goal from out wide, but easy goals from tap in was missed because they had nobody in the box.
Many coaches who have options in the team would just shift Henry out wide. They need a central forward who occupying opposition CBs, the discipline of a CF. Pep despite wanted to rid Eto'o, would still prefer Eto'o as CF over Henry. In direct comparison, Henry would be considered a better player than Eto'o and is as productive, and even having more tools.
Henry got subbed at half time after scoring goal but disobeyed Pep's game plan:
Eto'o ain't expected to stick between the CBs all the time either, recalling the the painful memory of his goal in Rome against us. The point being CF would play with opposition CBs mind all the time. CF stays central to receive ball to shoot, or to act as hub to lay off, or simply a decoy. CF moving wide from central position, should CB following him or leave him be. Great CF make CB think non stop.
Anelka fills that CF naturally perfectly just like Eto'o. At young age, Anelka was already at top level for a CF, with room to spare for growth. He may not be as explosive as Henry out wide, but he's capable of that Eto'o Rome move on more consistent basis.
People may wonder about false 9 when we bring up the topic of #9 and Henry habit of dropping deep. There has been this misunderstanding that false 9 is a CF dropping deep. Martial, Benzema, Firmino , Cavani even referred as false 9, which can't be more wrong. These guys are always forwards. False 9 is a system with no CF. So the goal scorers main starting positions can be wide forwards, no 10, central midfielders... The wide forwards role would be strict about holding position wide until final third according to Pep's philosophy. Same about no 10, midfielders. In final third, anyone can arrive in scoring position/ CF area. Henry likes to go wide, or drop deep, has play making ability also. However, he likes to roam, and he can't stick in central midfield forever to be a no 10, or midfielder; so to maintain a discipline to the system, Henry is the type that needs to be instructed to solely keep wide forward position in Pep team.