What do you think is the best opening for black after e4?

french or sicilian

1...e5

best by test

c5

Most would say the sicilian is the best. According to the recent pole it is also the most feared responce to E4. I prefer the Accelerated Dragon, but there are countless ways to go with the sicilian that give black a strong game. 

c5

1. Unequivocally e4 e5.  The open games are at the same time the most aggressive, and most solid and objectively best response.  There are many different ways to play the black side to suit whatever taste you might have (everything from the Petroff to the Latvian Gambit).  The one down side is you have to be ready for a lot of different openings like the Kings Gambit/Scotch/Italian etc.

2. Sicilian: I have never liked the sicilian because against solid play by white, its hard to get activity, especially in lines like c3 sicilian, and KIA.  Sicilian would be great if you could guarantee that white would play the main lines. But there is the other drawback: too many theoretical lines to memorize, and you can get smashed by a novelty.

3. French: Solid but passive.  I used to play the french. The exchange variation is too boring, and in a lot of lines you have to sit there and get beat up with no couterplay.

4. Caro-Kahn: Even more solid than french, with no blocked in Bishop, but hard to get an active game

5. Scandinavian: You can either get a type of caro-Kahn structure with Qxd5 or go all out with Nf6.  The ICelandic gambit is interesting and difficult to meet.

6. Pirc: The most annoying defense.  It doesn;t lose by force, but the only way you are going to ever win is if your opponent tries too hard to kill you in 20 moves.

7. Alekhine: Crap. I dont think this opening is good against anybody. Against a weaker player you are better off playing normally, and a stronger player will know how to crush you.

For anyone who feels the need to ask this question, the only correct answer is 1...e5.

Sicilian Defence.

sicilian is most annoying thats for sure

I don't understand why so many people hate/are afraid of the sicilian as white. Just man up and play the open sicilian. There are plenty of great attacking lines for white, and at amateur level, black needs to know his theory much better than white does in order to survive.

When I played 1.e4 I found that more offbeat stuff like the Alekhine or certain lines of the caro-kann were more of a pain than the sicilian. The positions seem harder to understand in those openings, and you do not see them a lot. 1.e4 players probably get to play against the sicilian 40-50% of the time, so they certainly should be able to get enough practice in its mainlines, and learn some of the theory.

To answer the original question. The best is probably the sicilian if black wants to win, and 1...e5 if he wants to equalize and is happy with a draw. At least that is how it seems at the top level. At amateur level, it does not matter. Play whatever you like, as long as it is sound.

This. At the amateur level, the Sicilian is generally bad for black. Black needs to know a ton of theory and usually grants white all the early initiative. Many of the Sicilian lines involve black patiently and accurately defending white's attack and then launching a counterattack, and defense is frequently the worst part of our games at this level. All white has to do is not panic and push his initiative.

Down here in Class D-B Land, the Sicilian is exactly what I hope to see against opponents of similar ability.

Hang on, you can't just ask a someone from Poland and decide that's the truth.

a5  

It does, of course, depend on the players, but if you're asking for my opinion, I'd suggest the Sicilian. I'm currently learning (and trying out) the Lasker-Pelikan variation. I'm using Kasparov's Revolution in the Opening (from my local library).

In my opinion, the Sicilan is a good choice because it's mostly black who chooses his pet line, and it's a nice attacking game. You have decent chances even without knowing theory and just applying general principles.

If I play white, the Damiano Defense. If not, 2.d3 allows me to go for a reversed KGD setup.

Try the dragondorfvariation of sicilian