What about his performance has been luck? Last year, he was the World Champion despite some mistakes, a lot of poor reliability and the occasional brain fade. This season, he has upped his game and is walking away with the championship for now. Out of the first five races, he was won four and taken a second place (and that was only the strategy that cost him the win).
So far this season, he has stepped up his game to levels the others are finding hard to cope with, he has shown incredible speed, better racecraft and is utilizing strategies well. More to the point, other than a practice crash at Turkey (which he bounced back from), he has not made a single mistake and is generally a class above the field. He has shown that he can overtake and defend.
So having said all that, I await your response as to where he has been lucky.
Well,during the current season Vettel hasn't found mayor logistic or extraordinary problems while in race,while Hamilton,Button and specially Webber found themselves in pretty bad situations,if you consider the Webber's pace on the last races you find that he manages better performance but he ends up losing when a situation like a mechanical failure comes up,the same can be said about Hamilton and Button,I'm not questioning Vettel performance,he is the very best driver on F1 currently but is not entirely the reason of why he is leading this championship season.
As for Alonso,he doesn't maintain consistency,I mean,he can be very brilliant on some part of the race,but keeping both pace and performance is what makes a great racing driver,he can have some good performance moments,but he doesn't keep up the pace for a whole race,Which brings me to imagine what can Kobayashi achieve in a race car like Ferrari's,is not to hard to consider the pace that Kobayashi manages through an entire race,which in,my opinion would be better than Alonso's pace and performance.
That's what I consider Alonso as an overrated driver,while there is more drivers with way more potential than him.