that is a HUGE question. that's like: i want to talk about european politics from the renaissance to present day :)
the sicilian is good for one reason: you exchange your c pawn for the d pawn. this creates huge imbalances that are present for the res of the game. notably - fight for d5, half-open c file vs. half-open d file, and white's difficulty controlling e5.
i just wanna talk about the sicilian. why do u think it's good why do u think it's bad what do u think is more favorable for black. if u think this is the best for black what do u thinkwhite should do. after Nc6 d4 or nc3 or whatever u think white should do.