There is no debate that Sturridge has scored at a phenomenal rate at Liverpool. There is no debate that the team will be organized in such a way for him to be put in the same sort of positions to score. But strikers go through purple patches where they score at a much higher rate than is their average. Papiss Cisse at Newcastle scored at over a goal a game when he arrived and now scores in 1 in 7. we all know about Fernando Torres.
Sturridge has scored at about one goal every 2.5 games in his career, including his time at Liverpool. Before Liverpool he scored at less than one in three (which is why he was sold). He's in his prime, playing in his best position that results in the most scoring opportunities so I expect him to score at a rate better than his career average, but the most likely thing is that he will not continue to score at this phenomenal rate. Thirty goals in a season is better than the top scorer in Italy has ever done.
Maybe Sturridge becomes one of the top five players in the world, I certainly hope he does, and he has the skill set to make that possible. My only hope is that should he simply be a very good player, which I think is the most likely thing to happen, that people aren't disappointed by his performances.
I don't think he needs to be one of the top five players in the world to get 30 goals in a season. Shearer never was. Rush never was. Personally, I think he'll get close to that in all competitions, with twenty or so in the league again.
He's not playing in Italy, so I don't see the relevance, it's a different footballing culture over there, the big teams will traditionally try to defend a 1-0 lead rather than go out to smash someone by five or six as we're doing at the moment.
As for career best vs current best, the best guide to a striker's form is usually the previous season, especially if he remains at the same club under the same manager, in the same role. He's at an age where strikers tend to improve rather than peak. If you look at how he was used at his previous clubs, you'll see that he was either very, very young, or played wide or (at Bolton) prolific.
He has everything going for him this season, there is no rational reason at all to believe that his conversion rate will suffer, the only question is whether he will get as many chances. We've added players in Markovic and Lallana who specialise in providing chances. We've seen in the recent past that he actually scores more often without Suarez in the side.
Eighteen months of consistent performance is not a fluke. 35 goals in 49 games is not a fluke.