Thanks for a comparisson, I've played MY City with my family and we really enjoyed the game, although we don't like legacy games. My Island still has rather low rating at BBG, but I was curious if it's becouse it's not that good or just becouse it's just new title. I guess we'll give it a try :)
You can only really replay with 2 players, as you get 4 boards and exactly enough stickers for 4 players. So after playing through once, you just use the other two boards. Also the "eternal game" that you can play after is just using the backs of the boards.
We think it's best at 2 player. That way you get to play through twice, and extra players really don't add anything because you are really just worried about your own board.