I did this lesson with my 1st and 2nd grade high schoolers but I think it can easily be adapted to other grade levels. The students really enjoyed this lesson and I actually had students participating that rarely do more than sleep. I think the key is that each student can work to their own ability.
So first I introduce the concept of comparatives with the powerpoint and then go over the rules for changing the adjectives. We then practice a few before also practicing the comparatives. I show them the slide "Which are better, dogs or cats?" I then write on the board "_____ are better than ______ because _______." I write the students answers in and help them come up with a because ________. Then I show them the next slide "Which is easier, Korean or English." I again write on the board "_______ is easier than ______ because ________." Of course they will all yell "KOREAN!!"
After these examples I start the activity. I start by asking them "Which is more dangerous, bmx or skateboarding." I then show them the videos of each. I usually showed them about a minute of each but the ones that they were more into I usually let play a little longer, use your discretion. After I show both videos I have them write on a piece of paper "______ is more dangerous than _______ because ______." My lower level students would generally only write the first part and leave the because blank while my upper level students would work really hard to express their opinions here. I would continue with this for the rest of the slides so that they had 6 sentences on their paper. When we were all finished I asked them their opinions about each of the slides they had seen.
I hope you guys like this, it's not the most challenging of all lessons but it got good participation and it kept the students' interest. Another bonus, after the powerpoint is made it doesn't require any prep work. Good luck!