Schumi can never ever be described as being the best ever because there was always the question regarding his team mates, Schumi was always contracted to be number 1.. the team mates role was to support him, this has been stated by Rubino, Irvine and others and at various times they have gifted him wins either by moving over or by holding up the progress of the competition thus making his statistics flawed.
Senna never demanded to be number one and he came into the Mclaren team against the standard setting Prost and beat him fair and square.... Who has Schumi raced against in the same team, what team mates of Schumi's have gone on to great things themselves ?

A good driver,a clever driver, a calculating driver... yes... the best NO

A test means nothing as do you not know the test procedure of all the teams or what they were working on, or the fuel loads being used....so what Ferrari did a PR exercise for the sponsors, its no different to when they got schumi to ride the ducati !!!!
I still think Kimi would have beat him if they were team mates !