It can be good, it can be bad...
Sicilian defence-Good or bad?

It is clearly sound.
But at a level below 2000 chess.com, there is a lot to learn. I have just played an Otb sicillian game against a 165 bcf graded player and he clearly didnt know his opening well enough.

Is the Sicilian defence good or bad? I've heard it was good and it was bad. What do you think?
I believe it to be the best reply to 1.e4. statistics seem to agree. so its very, very good.
but I think its bad for players u1500 to learn. better are double king pawn

The Sicilian Defense is accepted as the best response to 1...c5. Apparently, one of the main reasons why 1.d4 has a higher win rate for White than 1.e4 is because of the Sicilian Defense. It has tons of variations that are played at the highest level including the Dragon, Najdorf, Dragodorf, Sveshnikov, Classical, and Scheveningen variations.
In short, it's good.

Good and complex. I figure the Sicilian is still down the road for me in my chess development, as far as choosing to play it as Black; for now, I still respond 1...e5 to 1.e4 when I play Black.
Of course when playing White, no matter what your level, you have to have some basic ideas of how to respond to 1...c5 if you are a 1.e5 opener.
The Sicilian Defense is accepted as the best response to 1...c5.
I will ignore the misnomer but can you give us some factual statistics to back up your "accepted as the best response?"

The Sicilian Defense is accepted as the best response to 1...c5. Apparently, one of the main reasons why 1.d4 has a higher win rate for White than 1.e4 is because of the Sicilian Defense. It has tons of variations that are played at the highest level including the Dragon, Najdorf, Dragodorf, Sveshnikov, Classical, and Scheveningen variations.
In short, it's good.
Actually I think the reason 1.d4 is played more at higher levels is because the petroff defense is so drawish. But if black needs to win the sicilian is a good option.

The Sicilian has so many variations, each very different from the others. Most (if not all) are very sharp for both sides. This can be either good or bad. If you're really well-prepared you'll have a nice game. If you're not you might have to face strong attacks by the white player.
najdorf = good
all other sicilian lines are inferior
White wins after 2 c3
I would classify both these statements as bravado; useless opinion without statistical evidence or fact. Any opening is in fact a winner and a loser depending on a myriad of factors. The Sicilian is just an opening, no better or no worse then any other.

Any opening is in fact a winner and a loser depending on a myriad of factors.
I second that! Even the Damiano's Defense had some success - somebody drew with it against Fischer in a simultaneous game.
The Sicilian is good for those too cowardly to play the French, against which White has no hope of escaping defeat and utter humiliation.
The Sicilian is good for those too cowardly to play the French, against which White has no hope of escaping defeat and utter humiliation.
Not true! I've defeated people as white and they played the French!
In his book Chess Openings for Black, Lev Alburt recommends the Sicilian, and so I play it. It is good if you have a sharp tactical sense. Some are scared off. Like someone already said, there are too many variations.

well for all that wanted actual stats, here they are:
c5 is the most popular response to 1. e4 for Masters, by almost 100,000 games.
The win/draw/loss for black is almost split into perfect thirds for 1. e4 c5, about 6% leaning more towards white.
c5 is much less popularly played against anything else, and the numbers are quite down from 1. e4 concerning win/draw/loss percentage.
Personally, I like the sicilian, but I don't know a whole bunch about the line.
Is the Sicilian defence good or bad? I've heard it was good and it was bad. What do you think?