It's just boring to ignore context though. Greatness is more than just pure physical attributes and takes into account when and where they played and what obstacles they had to face, in football for example the quality of the pitches, shoes and the ball and of course much more.
To give you a different example to your Mercedes SL one: Do you think every sprinter who runs faster today than Jesse Owens did in the 30's is a greater sprinter than him? I'm sure there are many who can ran 100m faster than 10.2s today, but their achievements are totally meaningless in comparison. Ignoring the context of achievements in sports is really the most boring way to look at greatness, at least for me. Sure, an average modern sprinter is faster than previous world record holders. He's certainly not greater though. How a player influenced the evolution of the sport, the impact he had on his team and on the public within his era plays a massive role in greatness, always has and hopefully always will.