Well, most game engines tend to have a scripting language of some sort and that's usually GC'd. The reason that works ok is usually if you're embedding a language you can control how much time is spent on GC (and in the language itself). Doing an entire game from scratch in a memory managed language, it's not so much that GC is slow, it's that it lacks adequate control. (I don't think it's a coincidence that a lot of the popular runtimes -- python for instance -- tend to be reference counted with GC mostly reserved for cleaning up cycles.) If you're concerned with performance, it's not so much that GC _can't_ be fast, it's that you really don't want to give up control on that sort of thing because GC spikes are really annoying to fix.