I find all this fascinating, mainly the discussions over who will go down as a great of the sport, comparing records etc, but most specifically the "hasn't won a title without the best/one of the best cars on the grid" talk.
I may be wrong here, and feel free to correct me, but the last person who to my mind won a title with a car that wasn't the best or very close second best car on the grid, was probably Schumacher in 1995? And even then the Benneton was 2nd on number of poles in that season, so it wasn't a mid-table car that he somehow won with, he was just a brilliant racer in a very good, but not the outright fastest car. I just think its a bit mad, Mika Hakkinen is a legend of the sport, his '98 title car claimed all but 4 poles, his '99 title all but 5 (poor Coulthard didnt score one, Mika had all eleven!), so is his legacy dulled because he won both his titles in a car that was right at the front of the field? Not in my opinion. I think its largely impossible in the modern era, with the reliability and aero precision of the cars now, for a car not quickest, or close second quickest, to win a title. Put Senna in a Force India and he might luck out and win a race every other season, finish on the odd podium, but as great as he was, hes not dragging it to a title because the cars are so refined.
Looking at Hamilton and Vettel (and Alonso if you like, both titles were in cars fastest or very close 2nd), I think both will go down as the best since those Schumacher/Hakkinen days, and by the end of this season, Vettel will either match Fangio, or they'll both have 4 world titles, an incredible achievement. Both have had big battles for those titles, both have switched teams and won races, Hamilton will likely break Schumachers record and have the most pole positions in history. Like them or not, they will both go down as titans of their era, and will likely be brought up from time to time, after all is said and done, as being among the top 10 or so drivers ever to race in F1.
On Hamilton not having to grind in a lower car before the McLaren, I actually find this a strange thing to throw at him. In my opinion, having to come straight into the sport, in a title challenging car, alongside the reigning double world champion who dethroned the Micheal Schumacher is a far, far bigger challenge than learning your craft in a crap backmarker car. Him then going on to finish ahead of said double world champion, in his rookie year, is all the proof you ever needed that putting him there was justified. All he would've done in a lower car, is what Verstappen and Vettel did, look a level above anyone else, like a generational talent, and get fast tracked up anyway. He might have scored a rare win, he might not, it doesn't matter, the guy came in and promptly overtook Alonso into turn one at his first ever race.
Quick bit on Hamilton v Button at McLaren, the total points haul is a story of 2012's awful reliability for McLaren, and Hamilton having a very poor last half of 2011. His record in qualifying is 44-14 to Hamilton, in races its 27-20 Hamilton, and if you dialled out mechanical issues for both drivers, Hamilton would've outscored him in points as well (in 2012 alone he lost 3 wins from this). Been a while since I saw a breakdown of the calculated total of points lost to mechanical issues in 2012, but I think Hamilton lost something mental like 140 points, to Buttons 19. I dont mean this to slight Button, who I think was a fine driver, but there's a very good reason why he isnt brought up along the names of Prost and Senna, and Hamilton sometimes is.