Slightly off topic, but Schumacher's brilliance was in being able to win when he first went to Ferrari in a car which wasn't competitive.
Don't forget 2 world titles in a Benetton widely regarded as nowhere near the level of the Williams car at the time, and in 1994 especially, one that 3 teammates (including accomplished drivers Jos Verstappen and Johnny Herbert) found near impossible to keep in a straight line.
Even his debut in a terrible Jordan car on a circuit he had never driven before was notable. He managed to qualify 7th, classic early Jordan reliability problems ended his race on lap 1 but he sent ripples round the F1 world with his qualifying performance. Enough for Benetton to sign him immediately.
He finished 3rd (and ahead of Ayrton Senna) in the 92 championship in a Benetton that was so far behind other front running teams, especially Williams, in terms of active suspension, ABS, traction control systems and gearboxes that it may as well as have been in a different race category. That year there were unofficial references to a two tier championship with many teams running V10 or V12 engines as well as some using the above mentioned aids. The Benetton ran a conventional V8 and none of the new driver aids.
Yes he had everything set up exactly the way he wanted it at Ferrari between 99 and 04, but that machine did not drive itself to break virtually all records. Eddie Irvine did a sterling job as a a teammate, as did Barrichello later, but neither got anywhere near the same out of the car as Schumi did. He was relentless, some say robotic, but it cannot be argued he was not a truly world class driver. I remember the very moment I knew he was different. Commentators picked up on how he had locked up going into a corner, and had the presence of mind in the nanoseconds between a small hiccup becoming a big issue or even a crash, to let the brakes off and allow the tyre to rotate again. Even though he lost time in the corner, he didn't have a huge flat spot that would cost him dear later in the race. Multiple other drivers were shown on the replays ploughing through the same corner with 1 or more wheels locked up for dozens of metres, all had to come in for new tyres earlier than planned.
In agreement with your point, between 1996 and 1998 his Ferrari was inferior to other teams, especially Williams and Mclaren, but he managed to accumulate more wins for Ferrari in 1996 than the team had managed in the entirety of the 90s up to that point, which is remarkable considering the car was incredibly unreliable and he didn't finish 6 races due to breakdowns.
His career spanned the eras of some of the best drivers of moderns times, and largely he saw away all comers. Hill, Villeneuve, Alonso, Hakkinen, Raikkonen and Montoya are some of the most talented drivers I've seen in my lifetime.
There were accusations of illegal car setups sure, notably the unproven claims about the traction control and launch systems on the 94 Benneton. But what goes around comes around, in the late 90s Mclarens infamous second brake pedal came to notoriety and propelled Hakkinen on his trajectory to 2 world titles. I'm sure Ferrari/Schumacher felt the extra pedal was just as unfair as other teams thought his 94 Benetton was.
If not obvious by now, I am a huge Schumacher fan.
Hamilton is not to everyone's taste, but it has been consistently shown that sports personality is not about personality at all, simply sporting achievement. It has to be Hamilton.
Ronnie has reached some very significant milestones in similar fashion to Lewis in the past year, and I would love for a snooker player to be recognised, especially THE snooker player of my time. Equally I cannot comprehend Tyson Furys journey back to the top, it seems impossible. This makes him a true great in my eyes, whether a super fight to unify all the belts ever happens or not, he's already achieved far more than anyone thought when he was pictured a few years ago looking like a small planet.
All that being said, it HAS to be Hamilton. Mansell and Hill won it in the 90's (Hill twice!) and Lewis has eclipsed both of their achievements combined.