Introduction PowerPoint with lots of examples. Followed by a line up game - students have to line up by height, birthday etc without talking then say "I am taller than _____."
Riddles - Kids loved these. I gave a picture with things. For example 5 fruits with their weights. I then read hints "I am heavier than an apple." and they had to guess which object I was. Feel free to add to it!
Give me four - I didn't have time to play. Students would see an image and have to write down 4 comparisons in teams. Then one comparison would show up and if they wrote that one down they would get a point. Only would work for a high level class.