On Android, 2048 is 0.7mb. Threes is nearly 30! Surely that factors into some people's decisions.
I wouldn't even think to check that. At 30mb, Threes isn't that big (Retina assets and all). I would certainly understand your point if it was 300, but that doesn't seem excessive.
I can only think of a single game I've run into on my iPhone that surprised me with it's size. I'm not sure what it was (maybe an old version of Scrabble?), but it was a word game that was hundred of megs and didn't have much in the way of graphics.