Best reply to d4 which equalises black from the opening

@Sarg0n many thanks ..you made your point clear :) Nimzo all the way !!

I agree with @CafeMorphy the Stonewall Dutch is a solid defense. I used to play the Benoni and Grunfeld but I found that those openings didn't work out very well for me. I found that the Stonewall Dutch is easy to learn, with black pieces developing around the pawns in the center. The only downside is a weakness on e5, but it is still my favorite response to d4.

At the very very top (>2700 players) these openings equalize easily and they are most solid against d4: Queens gambit declined, Slav defense, Nimzo, Bogo indian, Griunfeld. Super GM's get more advantage and better positions against: Dutch, Benko(this is very decent until 2700+), Benoni, QGA, KID(we see this rarely nowdays), tarrasch etc etc

Most solid defenses againt e4 on the very top level: Spanish, Najdorf sicilian, Sveshnikov sicilian, French, Caro-Kan. Elite try to dodge sicilian kan, philidor to name a few famous openings.

Now again, one can play anything like Carlsen, but theoretically not to give your opponent any chances with perfect play, elite super GMs play the openings that I mentioned. I play lots of ICCF correspondence and can tell you that theoretically even counter albin gambit equalizes (White can get 0.7 at most but it's not winning) but openings like this gives white more advantage and more chances, where the elite openings equalize 0.00

Sorry I meant 1d4 Nf6

It is all a matter of fashion. Some openings are shunned until some top player picks it up and gets success with it.
It is also a question of time. Kasparov gave up on the King's Indian Defence, because he judged it too much work to keep up with it and at the same time with the Najdorf Sicilian.
There is also a practical issue. The very top players play for a win with black against lower rated opponents, so they need an opening with counter chances, not one that equalises close to a draw.

I think that Benoni or KID should be fine. KID is agressive and usally leads to sharp positions, where you can equalize in my opinion. QID is nice too. Also the Slav, really solid and if you know the lines you theoretically don't have much trouble to equalize as in all defences.
If you want to throw everything for the window maybe you should try the Dzindzi-Indian.

@Kestony I think you are confused in some of the defences you said against e4. Sicilian Najdorf is no "solid". It looks for imbalances and really sharp positions, same as Sveshnikov. Almost every sicilian is like that, for agressive players with chances to attack.
For example Caro-Kann's positions are more quiet and fit solid and positional players.
Can you imagine Bobby Fischer playing the Caro-Kann instead of the Najdorf? I don't

if you want equal ....1) d5 QGD or Slav gives pretty much = game

Gary Kasparov and David Bronstein played Caro-Kann several times.
Sicilian is all about positional play: black exchanges a wing pawn c5 for a centre pawn d4 giving black good prospects in the ending but giving white attacking chances from his faster development.
Robert Fischer considered 1 e4 superior to 1 d4.
Asked how he would fare playing against God, he said he would have no chance playing black, but he thought with White he could hold a draw playing the Ruy Lopez. Then he took fright: maybe He plays the sicilian...

Back on topic 1 d4. Theoretically there is no good answer. 1...d5 2 c4.
Now 2...dxc4 yields the centre, 2...e6 allows 3 cxd5 exd5 exchanging a wing pawn for a centre pawn with advantage, as Kasparov has often demonstrated, 3...c6 blocks the natural square for the knight and hampers the development of the queen's bishop as well.
1...Nf6 2 c4 and now the Nimzo-indian defence gives up the Bishop's pair, the King's Indian Defence and the Grünfeld give up the centre.
White has a theoretical advantage in all lines, but black gets counterplay and a chance for equality.