I agree, you wouldn't want to do GTA5 in java...... However,
Minecraft is currently chugging away on my laptop at 512MB, and performing quite well.....Even low end laptops have at least 2gb, and most of the graphics is offloaded to the GPU. It is very possible to make things run in half the memory, and be very strict about deallocating stuff after you allocated them....reference counting, etc. But, one mistake, and you've core-dumped your app. It is much harder to make something using C, than Java....especially cross platform.
I would say Java is good enough, in this instance.