The best defence against e4 ?

with some more analysis i found a strong line for black in the
closed Ruy Lopez, namely in the Zaitsev variation.
After 9.h3 Bb7 (Zaitsev) 10. d4 Re8! 11. Nbd2 Na5 12. Bc2 black
usually plays c5 (transpositions in black move order are possible)
but what next ? For example, after 13.Ndf1 (or d5) black often
plays 13 .. Bf8, a good move, which after .. g6 (to prevent the
white Nf1g3 and then Ng3f5) makes the fianchetto Bf8g7 possible.

But black has an even stronger move, namely 13 .. exd4 !
Now after 14. cxd4, black can bring his knight on a5 back
to c6, and also later still can play Bf8, making it very hard
maybe even impossible for white to achieve advantage.

In fact, because of this defence, it might even be better
to play 10 d3. for white, or 9 d4 (Boguljubow) but
in these cases also no structural advantage is achieved.

What does this mean ?
Well, having analysed many white openings, it appeared
that in most cases with e4 white could achieve a slight
advantage. But not anymore in above line.

S.. is that black move .. exd4! a novelty ?
Well, not exactly, in the high level -Chessbase sponsored-
'freestyle' (man+computer) tournament in *this* year,
2006, Rybka, the topengine played this move against
the engine Goldbar and the game ended in a draw.

For my personal research, and the E-book better
chess opening play, it means that now other opening moves
as 1.d4, or Nf3, or even 1.c4 are fundamentally just
as good as 1.e4. A major change ?

Well not really, for beginners i still recommend
1.e4, even although you might encounter a defence
like the one give above, or difficult Sicilian lines.
Medium/tactical players probably could better
switch to a gambit repertoire, which even would
be sharper than a general 1.e4 repertoire
more about that later (i'm thinking about
listing a general gambit repertoire, when always
starting with e4, eg. 1.e4 d5 2.d4!? etc.

And indeed, advanced players can maybe better
use a more positional repertoire with 1.d4, but..
also with this move i believe not fundamental
advantage can be achieved for white, which
means chess indeed is a draw; as was expected
already many years by those knowledgeable in
the subject (and top-GM's like Anand and Karpov).