The island is closer, the shingeki comparation is all about the wall and the fact that the kids are cattle, while eren and the setting put the humans in the walls as cattle.
I think it is bit different. There are plenty of series which the characters stuck inside the somewhere (inside the wall or the orphanage or whatever). It is more of the characters were unknown about what's happening outside and they were unknowingly stuck inside (like this series, Godspeed, and The Island). For SnK's case, the characters are already well known what's happening outside world, that's why they decide to build the wall to protect themselves.
Furthermore, those characters are actually allowed to leave one at a time hoping they going to have happy ending (SnK is more of going out side to fight against the titans).
Finally, the characters from SnK (and Koutetsu-jou no Kabaneri) already well known about what's happening outside, so already have prepared themselves to fight against their enemy. On the other hand, for this series, their world is suddenly broken and the characters were forced put in the situation for survival within limited amount of time. That's a big difference.