A shared vision is better than a great vision which is not shared. 1. Correct 2. Wrong

A shared Vision is always a better option. Few reasons for this.

1. When a vision is shared there is scope for feedback from close aides. This will help to improvise the vision and also suggestions on means to achieve the vision.
2. When the Vision is for a company, you always need the entire team to work towards achieving the vision. Unless the vision is shared you cannot get support from peers/team members.

A vision cannot be become great unless it is shared with others, the criticism, appreciations, views makes the vision great.  A great vision is a shared vision.

It's a tricky question, because there could not right answer. But however, it's better to choose a shared vision. You know, when you can feel/touch something you can evaluate it and you can change it.

I'm agree that a shared vision is better than a great one which is not shared for the simple reason 

that the shared one has much more chance to yield the attended results because the concerned people are most likely engaged with a shared vision

Correct