I'd bet anything that if Adriano played as much minutes as either Pedro or Sanchez in that position this season, he would have had more goals. I don't doubt that for a second.
You are not making sense... Alexis and Pedro had awful seasons, but that doesn't mean Adriano would outscore them, because as said earlier, he wouldn't get as many chances as them...
Adriano plays as a pure winger, he rarely steps into the box when played in a forward position, as you can see from the many times when Pep played him there... He rarely cuts inside making off the ball movements to get into scoring positions therefore reducing his chances on goal, it's just not in him because he is mainly a LB and the endline/touchline is where he thrives... Thinking that playing him closer to the goal would result in more goals is very naive, as would be playing Piqué permanently as CF and expecting 30+ goals a season from him... And even if by some unbeknownst reason Adriano ends up outscoring Pedro and Alexis playing as a forward, it would speak more of how much Pedro and Alexis suck than how good a finisher Adriano is...
That said, Adriano is freaking awesome, his goals are very valuable because they are very unexpected, be it from a long range whip or a darting overlapping run... If he could stay healthy for a whole season that'd be great, having him as an alternative to Alba and Alves is crucial to our success...