[Grammar] most simple

[Unregistered]

the most simple, the best- is it correct?

 

[Raymott]

the most simple, the best- is it correct?

Is what correct?
Yes, you have typed two correct English phrases joined by a comma.

 

[albertino]

the most simple, the best- is it correct?

The simpler, the better. ;-)
The simplest, the best.
(Not a teacher)

 

[Raymott]

The simpler, the better. ;-)
The simplest, the best.
(Not a teacher)

The first could be a proper English platitude, but the second is not a form that's used.
So, "the more, the merrier" is good. "The most, the merriest" is not.