Is sicilian the best black opening ?

Do you think the best response to e4 is c5, with all the different possibilities (alapin, dragon, schvechnikov, rossolimo, ...) ?

idk

yes sicilian is the best response

for e4 it's surely the best but for d4 it's King's Indian Defence

No. The best opening against 1.e4 is 1...e5. It is the most sound of all responses.

Keep in mind - most sound and highest win rate are NOT the same thing. The Sicilian may lead to more wins for Black than 1...e5, but it also leads to more losses for Black while 1...e5 has a higher draw ratio.

Sisilian defends gread opening for black

There are no "best openings".

Yes, imo its the best

Depends on your goal from the opening. A purist will say that achieving equality as black is the primary objective. An adventurous spirit may want to disrupt symmetry and break open the center to create possibilities for combinations and tactics. A positional mastermind may hope to keep things closed with all the pieces staying on the board, with hopes to create advantage by outmaneuvering the opponent. If there was a right answer, nobody would play anything else.

This is the sort of question it's best to discuss in a bar with your friends while enjoying liquid refreshment.