Hmm, I'm not sure. I think Henry had a really bad first year, especially for his standards. Only in his second year we saw much better football from him. I remember well how he even wanted to leave Barca at the end of the season, because he was disappointed. If Dinho didn't leave, Henry was gonna move. But Henry can be excused because he was played in a completely unfamiliar role to him.
It was a very different Barca in 2004 though, not playing the same football this Barca plays, and Eto'o wasn't moving from a different country. He played in Spain for 7 years already before he moved to Barca. A fair comparison will be Eto's move to Italy.
Nah, hard to use him here. He was a bench player in his first season and he already had a (very bad) full season in Barca and the whole summer, before his good 2005/06 season. Larsson scored only 3 goals in his first season in Barca. That's hardly something to take into consideration in this discussion.
Also, no-one notes how Zlatan is playing out of his position. He was never a target man and he's deployed as one in Barcelona. It's just like Henry who was played on the wing in his bad season.
In Juve language....It's almost as playing Del Piero as a target man and Trez as a support striker.