Good idea vs good point

Question

1. Good idea;
2. Good point.

Is there any difference in meaning between the above expressions?

For me they seem to be quite similar and interchangeable.

Would you please let me know your opinion?

Answer 1

They can refer to more or less the same thing, but an idea and a point are essentially different.

An idea can be very broad, from "let's go for a swim" to "hey, I think I proved Fermat's last theorem."

A point is normally an argument to either support or attack an idea.

In some cases the two may be or may seem interchangeable, but in the following cases they are not:

I am thirsty; shall we go for a drink?
Good idea!

I would really like to eat something.
But in an hour dinner will be ready, so maybe you should wait.
Good point!

Who knows how we can get across the river?
Let's build a bridge!
Good idea! But we have nothing to build it with...
Good point. Maybe we should swim across then.

Answer 2

I think both are the same. But I think a “good idea” is more proper.