i meant for black not for white - sorry
What's the best opening for white against four knights game?
There are many variations here.
From my head white can play: Bb5, g3, a3 (underestimated move btw) and d4. Ofcourse white can also play Bc4 but black is okay there

I like 5...Nd4. Look up the games of Kramnik in this line.
can you give the specific line please?
though i have a feeling you mean the ruy four knights?

5...Nd4 Rubinstein's variation IMHO BUT....
did it ever occur to you that total strangers cannot tell what is the best line for YOU? A lot of what's "best" depends on your style, taste, preferences and playing strength. You need to figure out minor details such as if you like/dislike: open/semi-open/closed games, attacking/defending/counter-attacking, tactical or positional play etc.

I cant find reference to a four knight 5..nd4 anywhere
Try looking in the Game Explorer and then type "Four Knights Game - Rubinstein Variation" into a search engine...

I have also read that 4...Nd4 is the best move, but I prefer Bb4, as did Capablance. It is also recommended by Nigel Davies and Mihail Marin in their repetoire books.

wow!! so active forum with and so many good people, it's the first time i post on this forum, i used to ask on yahooanswers.com and i received 1 or 2 answers max, from now on I'll always post here, thanks to each and everyone of you!!
I play 4. .. Nd4 to. The mentioned intermediate move comes 1 move later. If white plays 5. Nxe5 black should not respond with 5. ... Nxb5 as white gets an advantage but instead blacks should play Qe7 leading to a equal game

A few comments.
Yes, I typo'd on my cell phone and meant 4...Nd4 and was assuming White was playing 4.Bb5. 4.Bc4 is a blunder and Black is simply better after 4...Nxe4. 4.g3 Nxe4 is also fine for Black although here White can at least go into reasonable stuff by declining the Knight.

A few comments.
4.Bc4 is a blunder and Black is simply better after 4...Nxe4.
No, it isn't. Actually, white is slightly for preference in the much quoted sequence 4.Bc4 Nxe4 5.Nxe4 d5 6.Bd3 de4 7.Bxe4 Bd6. White should concentrate on pressure against e5 by 8.0-0 0-0 9.Re1! Re8 10.d3 Bg4 11.h3 Bh5 12.c3, where common sense says that white has a slight advantage.
But Black may deviate with 7...Ne7!? which opens up a lot of very tricky tactical variations.
Check your facts better next time, please.
i play four knights game a lot, as white and as black, against any opponent, but it's time to learn new stuff so what's the best defense against four knights game?