I think that "most used" could and should be distinguished from "most popular." I learned Objective C solely in order to make iOS games... out of the 12 or so programming languages that I've worked in, it's almost certainly the hardest to learn and the hardest to work in.

In retrospect I wish I had skipped learning Objective C and instead gone with a C++-based engine such as Marmalade, or a cross-platform development engine that would let me work in a language I actually like - such as C# in Unity, or ActionScript 3 in a Flash AIR mobile app. None of those were really viable options back in 2010 however. It's definitely the path I would recommend to game devs these days.

Of course portability is the biggest reason to not use Objective C... and this was the real reason that Apple probably encouraged it so strongly (and even, at one point, required it in their developer licensing agreements). The harder it was to port a game to other platforms, the stronger their lead over the mobile/tablet app market became.

I learned Objective C solely for iOS development and found it pretty ugly and ridiculous in the beginning but now that I've been using it for a few years it has grown on me. I am surprised that Java is ahead since that's the language I use the absolute least amongst C, C++, ObjC, and Java.