Niki was one of those greater than life characters, his outlook on life - especially after his famous accident - has always been an inspiration for me.
As an F1 fan, I will also miss his candid commentary on the F1 circus.
His grit, came back from a near-death burn injury in _six_ weeks to finish off the F1 season. The movie Rush (2013) made it more known in the popular culture.
To add to what others have said, "used to be a racer" is impressive in and of itself. It's a profession where almost every day they push themselves and an experimental machine to the limits, it's quite inspiring to see people brave enough to do that.
And then of course he did this so often and so well that he was world champion 3 times and came close a couple more times.
"A racer" undersells it a bit. He was a multiple-time world champion in what is arguably the "premier" motorsport, including twice _after_ suffering massive burns in a crash that should have killed him. If you made a list of the best race car drivers in history, there's no doubt he'd be on it.
Saying "I don't mean any disrespect" does not grant you carte blanche to speak nonchalantly about a recently-deceased motoring legend's life achievements.
As an F1 fan, I will also miss his candid commentary on the F1 circus.