Maybe inspired or stole the core concept, but 2048 is, to me, much more fun than Threes (I've logged a couple hours on Threes and many dozens of hours on 2048; I paid for Threes and kinda hate the 2048 app I use but it works - it's not the "free" quality of 2048 that keeps me playing it).

It's fair to say 2048 is a shameless rip-off, but that doesn't mean it's not better in ways that matter.