Two Thumbs Up was born out of a need to express and extreme delight in a situation / person / movie / music / etc etc.

If something is good it gets a thumbs up.

if something is indescribably brilliant - it gets a 'Two Thumbs Up'

But it's simply not good enough to just say the phrase - you must also physically represent the Two Thumbs Up in a strong motion with both hands.

To be used sparingly.