I think Barkley gets away with alot more because he's a local lad and everyone is hoping he's going to be our best CM for a long time to come, which I totally understand. Stones hasn't really had a bad performance as you said apart from the Derby, but he has made a few mistakes which haven't been punished, probably why no ones mentioned it.
I don't ever think Lukaku will get 30 odd goals a season but I do think he will be in double figures most seasons barring injuries and depending on how good a season the wingers have in whichever team he plays for he could get close to mid 20s.
I think Gerry has got everything he needs to be a good winger, he just needs it to click into place. I think it will be when he's about 23/24 he will hit his prime. I could be wrong as i'm not exactly a scout or anything but I think he's too good to fall away into an average player.