user8037: Which give me more advantage two Knights or two Bishops ?. And what should I choose two Rooks or a Queen ?

user291: On average, two bishops are better than two knights, but there are plenty of exceptions (e.g., a closed position where the bishops don't have room to operate).
On average, two rooks are better than a queen, but there are plenty of exceptions (e.g., when the player with the rooks has a bunch of weak pawns that are easy for the queen to attack).

user7500: Read the article "Evaluation of Material Imbalances" by GM Larry Kaufman:
The Evaluation of Material Imbalances.
He says about the bishop pair:

The bishop pair has an average value of half a pawn (more when the
  opponent has no minor pieces to exchange for one of the bishops),
  enough to regard it as part of the material evaluation of the
  position, and enough to overwhelm most positional considerations.
  Moreover, this substantial bishop pair value holds up in all
  situations tested, regardless of what else is on the board. This large
  a bishop pair value is surprising because in the opening grandmasters
  will often give up the bishop pair to double the opponent's pawns or
  to gain a mild lead in development, factors which are generally not
  worth half a pawn [DH: Since at the very start of the game a tempo is
  worth roughly a third of a pawn - and more later! - it is worth losing
  a tempo to save the bishop pair, but if you can gain two tempo by
  giving up the bishop pair that may be worth it in the short run!]

Later, queen vs. two rooks:

Although many authors talk about queen and pawn equaling two rooks,
  this is only close to true with no minor pieces on the board; with two
  or more minors each, the queen needs no pawns to equal the rooks. I
  recall a famous Portisch-Fischer game in which Portisch "won" two
  rooks for Fischer's queen right out of the opening, but Fischer soon
  won a weak pawn and went on to win rather easily, despite the nominal
  point equality. In fact Fischer's annotations severely criticized
  Portisch for making the trade; Fischer understood very well that with
  lots of material on the board, the queen is every bit as good as the
  rooks, so once he won a pawn he was effectively a full pawn ahead.

His basic tables of values is:

Pawn = 1
Bishop pair = +½
Rook =  5
Bishop = 3¼
Knight =  3¼
Queen =  9¾


8037: <p>Which give me more advantage two Knights or two Bishops ?. And what should I choose two Rooks or a Queen ?</p>
 291: <p><em>On average</em>, two bishops are better than two knights, but there are plenty of exceptions (e.g., a closed position where the bishops don't have room to operate).</p>

<p><em>On average</em>, two rooks are better than a queen, but there are plenty of exceptions (e.g., when the player with the rooks has a bunch of weak pawns that are easy for the queen to attack).</p>
 7500: <p>Read the article "Evaluation of Material Imbalances" by GM Larry Kaufman:
<a href="http://home.comcast.net/~danheisman/Articles/evaluation_of_material_imbalance.htm" rel="nofollow">The Evaluation of Material Imbalances</a>.</p>

<p>He says about the bishop pair:</p>

<blockquote>
  <p>The bishop pair has an average value of half a pawn (more when the
  opponent has no minor pieces to exchange for one of the bishops),
  enough to regard it as part of the material evaluation of the
  position, and enough to overwhelm most positional considerations.
  Moreover, this substantial bishop pair value holds up in all
  situations tested, regardless of what else is on the board. This large
  a bishop pair value is surprising because in the opening grandmasters
  will often give up the bishop pair to double the opponent's pawns or
  to gain a mild lead in development, factors which are generally not
  worth half a pawn [DH: Since at the very start of the game a tempo is
  worth roughly a third of a pawn - and more later! - it is worth losing
  a tempo to save the bishop pair, but if you can gain two tempo by
  giving up the bishop pair that may be worth it in the short run!]</p>
</blockquote>

<p>Later, queen vs. two rooks:</p>

<blockquote>
  <p>Although many authors talk about queen and pawn equaling two rooks,
  this is only close to true with no minor pieces on the board; with two
  or more minors each, the queen needs no pawns to equal the rooks. I
  recall a famous Portisch-Fischer game in which Portisch "won" two
  rooks for Fischer's queen right out of the opening, but Fischer soon
  won a weak pawn and went on to win rather easily, despite the nominal
  point equality. In fact Fischer's annotations severely criticized
  Portisch for making the trade; Fischer understood very well that with
  lots of material on the board, the queen is every bit as good as the
  rooks, so once he won a pawn he was effectively a full pawn ahead.</p>
</blockquote>

<p>His basic tables of values is:</p>

<ul>
<li><p>Pawn = 1</p></li>
<li><p>Bishop pair = +½</p></li>
<li><p>Rook =  5</p></li>
<li><p>Bishop = 3¼</p></li>
<li><p>Knight =  3¼</p></li>
<li><p>Queen =  9¾</p></li>
</ul>
