How would you translate the following sentences?

1) I wish I had gone skiing.

    I wish I went skiing.

     I wish I would go skiing tomorrow.

2) I wish he had gone skiing.

    I wish he went skiing.

    I wish he would go skiing tomorrow.

1) I wish I had gone skiing. - Keşke kayağa gitseydim.

    I wish I went skiing. - Keşke kayağa gitsem.

     I wish I would go skiing tomorrow. - Keşke yarın kayağa gitsem.

2) I wish he had gone skiing. - Keşke kayağa gitseydi.

    I wish he went skiing. - Keşke kayağa gitse.

    I wish he would go skiing tomorrow. - Keşke yarın kayağa gitse.

hmmm my guess:

I wish I had gone skiing. - Keşke kaymış olsaydım.

I wish I went skiing. - Keşke kayağa gitseydim.

As a native I can say Aurum´s answer is true. 

But, I wish I went, is past tense. 

I wish I went, I wish I had gone, are often interchangeable

I think it depends on the context:

I wish I went skiing today - gitsem

I wish I went skiing last winter - gitseydim

In English I guess you wish in the past tense even if you want it to happen now. But in Turkish it is not so. The wish mode -se/sa doesnt have time or a tense in Turkish. It is timeless. But you can use past tense after it and that way you can express the time. You cant use other tenses after or before it.

How about ´I wish I COULD go skiing´?

Kayağa gidebilmeyi isterdim

Keşke kayağa gidebilsem.

Thanks. Could have known that.. :/