Now, I never saw a lot of these guys race, so I'll base this on some reasonably extensive reading. I'll try to provide one positive and one negative aspect of the career of each.
Rindt - Hardest man on the list to rank, as he was killed far too soon. Clearly blisteringly fast - enough to easily beat Brabham in the same car. As I say, died too young for a reasonable assessment of his place in history, although rumour has it he would've retired at the end of 1970 anyway.
Stewart - Probably one of the ten best drivers ever to sit in a Formula 1 car. Hard to rank him down, really - perhaps one could say Graham Hill at a slight edge over him at BRM, but he was also vastly more experienced.
Fittipaldi - Achieved an awful lot very young. Really good record in the States as well. Highly talented, but a bit like Michael Owen - you expect him to push on and get better, but he doesn't. Also hand-grenaded his own career by pootling around in his brother's team for what might have been his peak in the late seventies.
Lauda - Perhaps the hardest bastard ever to sit in an F1 car. A personal favourite of mine, almost every aspect of his story is characterised by extraordinary determination. From buying his way into the sport to coming back from his accident to returning after a two-year hiatus and overcoming the faster Prost in the same car. Combustible - falling-out with Ferrari probably cost him a title or two, and he was definitely slower than Prost at Mclaren - but he was really, really quick early in his career. Underrated nowadays.
Hunt - Interesting character. More like Raikkonen than we give him credit for - extremely quick, but with a very definite peak and a spark that began gradually to dim after he won the title.
Andretti - A man of incredible achievements on both sides of the Atlantic. Not only instrumental in the development of the ground-effects Lotus, but also quicker than people give him credit for; he usually outqualified Peterson in 1978. Another driver it's difficult to criticise. Perhaps if he'd been more focused on F1 throughout his career he could have achieved more, but then, it's not like he wasted his time in America...
Scheckter - Pretty underrated. Villeneuve was probably a bit quicker, but Jody hardly disgraced himself, particularly on the days when the car was tricky. Crash-happy early in his career and seemingly gave up once he won the title, though. Could have achieved more - not many people realise he was actually younger than Villeneuve.
Jones - Bit like Hunt, really. Really fast (fast enough to win a race with an unlikely team), but a combustible character who's career began to wane after he won the title. His comeback was a real shame, as well.
Piquet - Sometimes maligned on this board, but he must have had something. Performances in the early eighties very strong, but kept on racing for too long. Perhaps he was never as quick as Mansell, but then, not many drivers are. Quite often his attitude stunk as well.
Rosberg - Hate to say it but a bit lucky. Took his sole chance to win a title well, (although he wouldn't have won it without Pironi's crash) and was unbeatable on his day, but his 'day' wasn't as often as some of the drivers on this list. Found out when paired with a top-class teammate (Prost). Bit like his son, really.
Prost - Clever, hard-working, and faster than he's given credit for. Outpointed Senna during both of their seasons as teammates, although he wasn't as quick (but then, who was?) Fantastic title in 1986 and was good enough to be WDC at the age of 38. In the era of the ego, though, he certainly had one, with acrimonious departures from Renault, Mclaren and Ferrari.
Senna - What to say? Maybe the fastest driver of all time. I wouldn't like to rank the quadrangle of Fangio-Clark-Senna-Schumacher but I'm quite confident in saying that they're better than anyone else to do it since 1950. Downsides? Well, he did used to make some mistakes and in the era of ego, his was the biggest of all. The apparently premeditated ramming of Prost at Suzuka in 1990 was probably the most disgraceful thing the sport has ever seen. But goodness, what a talent he was.
Mansell - A late burner, but he burned bright. Fantastic overtaker, balls like melons, one title a poor showing given the quality of his performances from 1985-1992. Had longevity as well - won his final race aged 40. Downsides would be a ginormous ego and the fact that he didn't set the world alight at Lotus. But a great driver all the same.
Schumacher - See Senna. Astoundingly, astonishingly, sometimes unbelievably fast. Outstanding longevity (good enough to win a race for sixteen straight seasons) but, like Senna, sometimes downright dirty. Senna excepted, though, put him in a car next to anyone else in this list and I think he'd come out on top. Senna's death robbed us of a fantastic rivalry between the two.
Hill - Good, honest, hard-working driver who gave his all. Thoroughly decent bloke. Flattered by his machinery.
Villeneuve - Made an incredible debut, but aside from that... Also flattered by his machinery, and lucky to be a WDC.
Hakkinen - A late-burner like Mansell, but underrated nowadays nonetheless. His form from 1998-2000 would have put him right at the sharp end in any area. Also the best racing driver I've ever seen under pressure; his three consecutive Suzuka performances with titles on the line were outstanding. Perhaps struggled to motivate himself when he didn't have a title-challenging car - can't be a coincidence that the seasons in which Coulthard was able to beat him were the seasons in which they were never going to win a title.
Alonso - I think 'Prost-lite' is a fair analysis. He's smart, he's deceptively fast and he's the best driver of his generation. Like Prost, though, he's fallen out with three teams and it's hurt his career. Would be a travesty if he doesn't win a third title before he retires.
Raikkonen - Very fast, but needs the car underneath him. Seems to need the team behind him as well - with Ferrari giving equal focus to Massa, Alonso and Vettel, he's struggled. At Mclaren, at Lotus and in the latter halves of 2007 and 2009, with a team behind him, he was awesome. Still, good enough to be very competitive at 37, so he's definitely still got something.
Hamilton - Fast. Very fast. Increasingly mature, too. Does let his head go down when things aren't going his way, but he's in the best form of his career and it'll be interesting to see how well he drives these next few years, which ought to be his peak.
Button - It's funny. I didn't really think he looked like a WDC even when he was winning the title. It was afterwards, in 2010 and particularly 2011, when he started to suit the role. Since then, he's been a terrific driver, perhaps the confidence his title gave him helping out. Not by any stretch the best driver on this list, but I certainly think he deserves to be on it.
Vettel - I like him a lot. His victory at Monza for Toro Rosso was one of the most impressive I've ever seen. Niggling doubts about his ability to perform when the chips are down and his speed next to Alonso and Hamilton, but then, all drivers have off weekends. Good enough to be world champion again, that's for sure.
