GL is practically a gimme on Immortal if you want it. The AIs rarely prioritize Aesthetics and Literature - often if you don't build it then it isn't built until after 500AD. If you research Aesthetics after your worker techs you will get it. Its a very powerful wonder - by itself it practically guarantees that you will be first to Liberalism since that city can then have four scientists and the GPP from the wonder - it will pop out at least three scientists in time allowing you to get Academy + Philo + Education. Its expensive to build - my rule of thumb generally is not to bother with expensive wonders unless I am industrious or have the necessary resource. If I have stone I will consider Pyramids and if I have marble GLH. If industrious both of course.