I wish I could = I wish I were good at ?

"I wish I were good at" could also mean there is something you can do well enough, but aren't really good at.

I wish I could sing.

I wish I were good at singing.

Using your definition ("the ability to do something that I don't have as for now," they could mean the same thing.

There are subtle differences, however.

It is different, for instance, you say "i wish i could have helped him" just to express kinds of regret,but" i wish i were good at helping him" does not have the same meaning.

I wish I could perform in that show.

I wish I were good at singing.


in the first example, one reason you might not be able to perform in the show is that you were not invited. It doesn't necessarily have anything to do with ability or qualifications.

the second example is all about ability.

Thanks for your helpful reply.

But I want you to see the following sentence,
"I wish I could sing well."
This is about ability, right? (It's extracted from a text book.)

So, am I OK to conclude that "I wish I could" is more widly used than is "I wish I were good at", which is used only in expressing ability or qualifications?

Thank you

Both are correct but it varies according to the situation.
I wish I could dance or I wish I were good at dancing.