Does your weight effect the amount of calories you burn?

Yes. It takes more energy for a larger person to move than for a smaller person to move.

I don't know how much I'd trust the accuracy of the wii calorie estimation, but generally speaking yes a larger person can burn more calories more easily than a smaller person. My husband and I workout together, doing workout dvds, we both have heartrate monitors calibrated to our own stats and while I might burn 250 calories in our workout he might burn 400 even though our heartrate averages and maximums are extremely close over the course of the workout. I'm 127 lbs, he's 190.

your weight definitely affects how many calories you burn. think of it this way, your lifting more weight if you're heavier so you would be working your body harder. its also easier in the beginning to lose weight if you are heavier. it sucks, but its true. the last few pounds are always the hardest to lose.